Choosing a UPS for a home setup Advice please.

[Sam Plusnet]

I lost a PC PSU to a couple of micro-power cuts and (no doubt the
associated voltage spikes etc.), so I decided to get a UPS to protect
things.

I only want to support the desktop PC, Monitor and my 4 bay NAS.

The next question is "How big a UPS do I need?"

I went looking for advice on this, and found most said:

"Add the PC PSU rating (850W in this case) to the NAS PSU rating (90W)
and the Monitor (78W) to get the max load (1018W) then multiply by 50%
(some say 100%) to give some headroom.
Some even pointed out that (e.g.) the PC PSU rating was its DC output,
so its AC input would be even greater so...

Things seemed to be getting completely out of hand, so I decided to
measure, not calculate.

I put those three items (PC, Monitor & NAS) on a separate supply circuit
monitored by a power meter set to record max power draw in watts (VA
would have been better, but that's what I had available).

Ran things up. Pulled video down from the NAS & ran it on the PC. Ran
up a few more apps at the same time - I did pretty much anything I could
think of to max out the loading.

Maximum recorded power demand 159W.

The difference between the recommended calculated load and the measured
load is so vast that I'm beginning to doubt myself.

I'm certainly not the first person to go down this route so... Comments
please.

--
Sam Plusnet

[John Walliker]

You have done the right thing. The rated power consumption of an electronic
product is based on worst case conditions. That means that every USB connector
will be delivering its maximum output power, the power supply will be driving the
most power hungry motherboard that it is rated for, every disc drive slot will be
filled. Back in the real world, these conditions hardly ever happen all at the
same time. Adding a decent safety margin - maybe 50% to 100% - to your
measured results will give you a reliable but not unduly over-specified system.
Load currents are generally highest at startup, but the UPS will normally be
delivering power to a system that is already running when the mains is interrupted,
so you don't need to worry about this too much.
You mentioned that your measurements are W not VA. Rated power is measured
in W, but UPS ratings are generally VA because it is often the output current that is
limited rather than the power. Devices with power supplies rated at less than about
75W may not need PF correction, but larger ones will have it. Maybe add 10% to 20%
to your measured power to allow for less than perfect PF.
John

[John Rumm]

On 20/02/2024 20:46, Sam Plusnet wrote:

> I lost a PC PSU to a couple of micro-power cuts and (no doubt the
> associated voltage spikes etc.), so I decided to get a UPS to protect
> things.
>
> I only want to support the desktop PC, Monitor and my 4 bay NAS.
>
> The next question is "How big a UPS do I need?"
>
> I went looking for advice on this, and found most said:
>
> "Add the PC PSU rating (850W in this case) to the NAS PSU rating (90W)
> and the Monitor (78W) to get the max load (1018W) then multiply by 50%
> (some say 100%) to give some headroom.
> Some even pointed out that (e.g.) the PC PSU rating was its DC output,
> so its AC input would be even greater so...

That all sounds a bit excessive...

What graphics card is in the PC?

> Things seemed to be getting completely out of hand, so I decided to
> measure, not calculate.
>
> I put those three items (PC, Monitor & NAS) on a separate supply circuit
> monitored by a power meter set to record max power draw in watts (VA
> would have been better, but that's what I had available).
>
> Ran things up.  Pulled video down from the NAS & ran it on the PC.  Ran
> up a few more apps at the same time - I did pretty much anything I could
> think of to max out the loading.
>
> Maximum recorded power demand 159W.
>
> The difference between the recommended calculated load and the measured
> load is so vast that I'm beginning to doubt myself.

Even a fairly powerful PC is unlikely to draw more than 250W
continuously. Probably less than 100W most of the time. The other things
not much - unlikely to be more than 100W all together. (note that inrush
can be much higher - so turning kit on while running on battery can
glitch the output enough to drop a load or reboot a PC)

So a 650VA UPS would likely be plenty, and leave some capacity to spare.
That kind of device is also fairly cheap.

Having said that you often find that as the VA rating goes up, at some
point so does the battery capacity. So if you only have 500VA max load,
it can still be worth going from the (adequate) 600VA to the (overkill)
1kVA to get the bigger batteries and double the run time.

(I recently wanted one to hold up a micro form factor PC (fairly high
end i7 box - running accounting software in 4 VMs), a synology NAS, and
various bits of network kit including a 24 port PoE switch).

I was looking at a CyberPower BRICs unit, and the 1kVA/600W would have
been plenty. However at half load the unit was only rated for about 6
mins. So going for the 1.2kVA version which has twice the battery size
gave plenty of time for the orderly shutdown of the NAS and all the VMs
if required. (in reality, according to actual load shown on the the
power meter on the UPS, it will likely get 60+ mins of runtime)

Something else to consider when supporting multiple bits of kit is how
you will synch the shutdown of the attached loads. Most UPS devices have
a USB connection these days that lets you connect a single PC or other
device and monitor it. That also allows you to specify a charge
remaining threshold when the device should power down. That is easy with
just one PC.

However it gets a bit more complicated with multiple devices. There is
an open source suite of software called NUT (Network UPS Tools), that
allows one device physically talking to the UPS to act as a server and
share information about the current power state with multiple clients. I
found the Synology box actually uses this for its default UPS monitoring
capability (although it does not seem to name it directly). That made it
easy to get a NUT client for the main windows machine running the
hypervisor, setup the NAS as the NUT server, and point the windows box
at that. That the whole lot can be gracefully shutdown in sequence, and
then finally switch off the UPS itself as well once the available
capacity falls below the desired capacity threshold.

(on restoration of mains, everything is configured to come back up can
carry on were it left off)

> I'm certainly not the first person to go down this route so...  Comments
> please.

I have an extension lead made up with exposed individual wires, so that
I can loop them through a clamp meter:

https://wiki.diyfaq.org.uk/index.php/File:MainsCurrentTestLead_(Medium).jpg

Makes a handy way to get a feel for the actual size of UPS required.

--
Cheers,

John.

/=================================================================\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\=================================================================/

[S...@home.com]

Amazingly, I have never required a UPS over thirty years of computing.

[Jeff Gaines]

On 20/02/2024 in message <Tc8BN.307810$Ama9....@fx12.iad> Sam Plusnet
wrote:

>I lost a PC PSU to a couple of micro-power cuts and (no doubt the
>associated voltage spikes etc.), so I decided to get a UPS to protect
>things.

When you've finished your calculations this is the modern version of the
one I have:

https://www.amazon.co.uk/APC-BACK-UPS-BE850G2-UK-Uninterruptible-Protected/dp/B0828G42KN/ref=sr_1_3?dib=eyJ2IjoiMSJ9.br4fFzBVpJA6Vt3vmBchQXARCrvm5q9E075DBvrtPbprDjYIxwhc0kOHf2NhTLAYrEKzSwQXOx690gQqrrVkUhc8W5It17O_kYNRibR-tyBMvWieZT_rgtS9VPI4Co4FmnFcaWSYSq95w4PPudLJ3PZO1Oz9Q3IKEQ6ORpdtvVh3cvGxFE6WPQcOGZpbestpbtrElwJrxJsv0JPzSTnJOlA12NhdfUXULPd1wdMomiM.WGESu0PS-H27OzadV8u7PF_7TO8QkE6jLxFGI3iLHog&dib_tag=se&keywords=apc+backup+ups&sr=8-3&ufe=app_do%3Aamzn1.fos.d7e5a2de-8759-4da3-993c-d11b6e3d217f

I've always lived in rural areas with overhead cables so power cuts are
frequent. I have it set up so as soon as mains power is lost the PC shuts
down, I don't expect it to run the PC in the event of a power cut.

--
Jeff Gaines Dorset UK
I can please only one person per day. Today is not your day.
Tomorrow, isn't looking good either.

[The Natural Philosopher]

On 20/02/2024 20:46, Sam Plusnet wrote:

You are nuts to put an 850W PSU in a PC that never exceeds 100W?

What you calculated was the gold standard 'this will *have* to work'..
Not the 'well this will, in practice work'

However there are *VA* ratings. The *peak* inrush current on your power
supplies may well be 4A if you switch them all on at once.

In short while the 'heating' power may well be down at 150W, the 'fusing
current' might well be up around 4A at mains voltage, or 80 amps from
the e.g. 12V car battery.

The question is whether or not your UPS can handle that for a second or two


--
"The most difficult subjects can be explained to the most slow witted
man if he has not formed any idea of them already; but the simplest
thing cannot be made clear to the most intelligent man if he is firmly
persuaded that he knows already, without a shadow of doubt, what is laid
before him."

- Leo Tolstoy

[The Natural Philosopher]

On 21/02/2024 05:48, S...@home.com wrote:
> Amazingly, I have never required a UPS over thirty years of computing.

Me neither, though there have been times I wished I had one.

--
Climate is what you expect but weather is what you get.
Mark Twain

[noth...@aolbin.com]

On 20/02/2024 20:46, Sam Plusnet wrote:

The simplest advice is to switch to a laptop with external display,
keyboard and mouse. I did that a very long time ago and have never lost
data for any reason.

[John Rumm]

On 21/02/2024 03:26, John Rumm wrote:

> (I recently wanted one to hold up a micro form factor PC (fairly high
> end i7 box - running accounting software in 4 VMs), a synology NAS, and
> various bits of network kit including a 24 port PoE switch).

> Makes a handy way to get a feel for the actual size of UPS required.

For a home setting, in town with reliable electrical supply, and not
doing critical work on a computer, there is only a marginal benefit to
having a UPS.

In a rural location with overhead supply where short power outages are
common, it becomes far more important. Same goes for if you need to WFH
often, or have other kit that may not take kindly to having the power
dropped on them without warning (NAS box, Hard drive PVR etc)

For business use (like that described above) where trashing a critical
database is not high up on the agenda of desirable outcomes" it would be
daft to not have one.

[SteveW]

On 21/02/2024 05:48, S...@home.com wrote:

If you run a home server, you don't want to risk corruption of the
storage array due to power cuts, brownouts or spikes, so a UPS is a very
good idea. Also useful to avoid having to restart the server if you need
to knock the power off for a few minutes during DIY.

As we are switched over to digital telephony, a UPS to keep the phone
working may become a good idea too.

[SteveW]

On 21/02/2024 08:25, Jeff Gaines wrote:
> On 20/02/2024 in message <Tc8BN.307810$Ama9....@fx12.iad> Sam Plusnet
> wrote:
>
>> I lost a PC PSU to a couple of micro-power cuts and (no doubt the
>> associated voltage spikes etc.), so I decided to get a UPS to protect
>> things.
>
> When you've finished your calculations this is the modern version of the
> one I have:
>
> https://www.amazon.co.uk/APC-BACK-UPS-BE850G2-UK-Uninterruptible-Protected/dp/B0828G42KN/ref=sr_1_3?dib=eyJ2IjoiMSJ9.br4fFzBVpJA6Vt3vmBchQXARCrvm5q9E075DBvrtPbprDjYIxwhc0kOHf2NhTLAYrEKzSwQXOx690gQqrrVkUhc8W5It17O_kYNRibR-tyBMvWieZT_rgtS9VPI4Co4FmnFcaWSYSq95w4PPudLJ3PZO1Oz9Q3IKEQ6ORpdtvVh3cvGxFE6WPQcOGZpbestpbtrElwJrxJsv0JPzSTnJOlA12NhdfUXULPd1wdMomiM.WGESu0PS-H27OzadV8u7PF_7TO8QkE6jLxFGI3iLHog&dib_tag=se&keywords=apc+backup+ups&sr=8-3&ufe=app_do%3Aamzn1.fos.d7e5a2de-8759-4da3-993c-d11b6e3d217f
>
> I've always lived in rural areas with overhead cables so power cuts are
> frequent. I have it set up so as soon as mains power is lost the PC
> shuts down, I don't expect it to run the PC in the event of a power cut.

Do you actually have it set to shut the PC down immediately or with a
couple of minutes' delay? The latter would allow for times when the
power cuts out, but reconnects shortly after.

[SteveW]

Definitely overkill - although on some (gaming) machines, little power
is used while watching a video, but when playing a game, the video card
alone can take 250W ... and some machines have a pair of video cards
working together. Unlikely for the sort of machine that might need a
UPS, at home, though.

[Jeff Gaines]

On 21/02/2024 in message <ur4o0v$33uk8$2...@dont-email.me> SteveW wrote:

>>I've always lived in rural areas with overhead cables so power cuts are
>>frequent. I have it set up so as soon as mains power is lost the PC shuts
>>down, I don't expect it to run the PC in the event of a power cut.
>
>Do you actually have it set to shut the PC down immediately or with a
>couple of minutes' delay? The latter would allow for times when the power
>cuts out, but reconnects shortly after.

The latter, hibernates after 3 minutes.

--
Jeff Gaines Dorset UK

There is no reason anyone would want a computer in their home.
(Ken Olson, president Digital Equipment, 1977)

[Paul]

For a PC, I use a copy of Furmark to max out the GPU. And
a copy of Prime95 or use 7ZIP compression, to keep the CPU busy.

On this machine, that would be 300W. Without the goading,
a "typical busy value" would be 136W, which is railing on
one CPU core, without the GPU in usage. That's the difference
a "power test setup" makes to the demand result.

On the other machine, it will draw 400W, 180W for the graphics card.
Most of the time, it runs 100W-180W if not goaded.

But the power meter is the right approach. Measurement as a
means to reflect some degree of reality. The NAS and the display device,
they might have more static loads for all I know.

I originally budgeted for one PC on the UPS, but eventually
had two on it. You would not expect too many cases where
they would go-to-max on their own. The UPS is disconnected
at the moment, because the battery is dead, and I did not
like the failure mode it displayed.

Paul

[The Natural Philosopher]

On 21/02/2024 11:03, noth...@aolbin.com wrote:

> The simplest advice is to switch to a laptop with external display,
> keyboard and mouse. I did that a very long time ago and have never lost
> data for any reason.

I doubt I could fit 4TB disk into a laptop.
My main server died yesterday. It was my oldest and worst *86 machine,
so I popped its disks into my second worst *86 machine and rebooted.
Apart from it insisting on using a DHCP network address because the
ethernet came up as a different device, it was in fact a straight reboot.

No data was lost.

Unless you have a *very* busy machine, power loss wont corrupt your disks.

UPS is more about having internet access during a power cut, for me.

--
“It is hard to imagine a more stupid decision or more dangerous way of
making decisions than by putting those decisions in the hands of people
who pay no price for being wrong.”

Thomas Sowell

[The Natural Philosopher]

It is very wise to either keep a PC up and shut it down gracefully, or
if you have limited battery, shut it down immediately. And keep it down.

The *only* time I ever lost data during a power cut was when a PC lost
power, the power came back on and it stared booting automatically, and
then a brownout crashed it again *as it was booting*. The boot disk
never recovered.

These days my machines go down and *stay* down. Until I am sure the
supply will last long enough to reboot them properly and check their
filesystems.

Shutting down an idle machine by pulling the plug on it almost never
corrupts its data.
But a UPS makes sure anyway.

--
You can get much farther with a kind word and a gun than you can with a
kind word alone.

Al Capone

[The Natural Philosopher]

Indeed. If I were to do all that I'd need to power a router, a server, a
PABX and a desktop PC in the office here with a separate UPS for the NTE
downstairs as well

That would still not be ideal, but I would have internet. But not a
central heating system...

--
"And if the blind lead the blind, both shall fall into the ditch".

Gospel of St. Mathew 15:14

[S...@home.com]

Most of my gaming computers are laptops now, with batteries for back up.

[Paul]

You do NOT want to mess up RAID arrays, by doing dirty shutdowns.
Yes, there are kinds of equipment you definitely want a UPS.

I've had people report all sorts of funky failure states for RAIDs.
Like the poor individual who had a RAID Mirror of two drives.
One drive died, the other drive had apparently "stopped mirroring"
three months prior, and he lost three months worth of changes to
his data. And people do not set up Mirrors, just for the aggravation
when they didn't work. They expect them to work.

RAID arrays still need backups. And a UPS helps prevent them
from becoming de-synchronized.

I do not really know what keeps consumer SSDs alive on power failures.
It's supposed to be a "firmware scheme", but since they don't have
advanced power fail detection (and a Supercap), it's not hardware
that protects them against critical data loss. It's hard to imagine the
flash has sufficient life for any sort of firmware scheme to make
the device "reliable".

The UPS can have a cable, which plugs into the PC, and it tells
the PC to do a shutdown. Typically this fires off at the
two minute mark (before the UPS has run out of juice). And it
allows the PC to do a clean shutdown.

Paul

[charles]

In article <ur4rge$34q74$4...@dont-email.me>,

My solar powered battery will allow me to use the boiler ;-)

--
from KT24 in Surrey, England - sent from my RISC OS 4t้ฒ
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle

[SteveW]

My UPS would not talk to my server (only windows was supported by the
UPS software and NUT never worked with it), so I had to resort to the
server detecting when it lost power on one of its dual PSUs - not ideal,
but it did work.

[Tim Lamb]

In message <ur4qvl$34q74$2...@dont-email.me>, The Natural Philosopher
<t...@invalid.invalid> writes

>On 21/02/2024 11:03, noth...@aolbin.com wrote:
>
>> The simplest advice is to switch to a laptop with external display,
>>keyboard and mouse. I did that a very long time ago and have never
>>lost data for any reason.
>
>I doubt I could fit 4TB disk into a laptop.
>My main server died yesterday. It was my oldest and worst *86 machine,
>so I popped its disks into my second worst *86 machine and rebooted.
>Apart from it insisting on using a DHCP network address because the
>ethernet came up as a different device, it was in fact a straight reboot.
>
>No data was lost.
>
>Unless you have a *very* busy machine, power loss wont corrupt your disks.
>
>UPS is more about having internet access during a power cut, for me.

As it is now 62 years ago I can tell a tale about UPS. Final year
apprentice, with a car! I was often sent to sites to stand by during
testing of our electrical equipment.
This occasion was the American Air Force. Communications set up with a
specification of 10mS interruption of supply only. Our device was a
transistor power supply for the windings of a permanently running
battery fed alternator. Might have been 50 lead acid batteries in that
room!
The test failed miserably. Basically the winding inductance opposed the
level of current change needed to maintain synchronous speed.

The solution was to fit a massive flywheel:-)

>

--
Tim Lamb

[SteveW]

With the addition of a changover switch for the boiler (and maybe
lighting) supply, our EV would allow that too.

[SteveW]

In the '90s I worked on the works testing of two 24MW generator sets for
a North Sea rig. In each control room was a huge stack of lead-acid
batteries to supply a DC lubrication pump (in an emergency shutdown, the
gas turbine front bearing would melt from residual heat without the
lubricating oil circulating). The requirement was to supply 22kW, at
110V DC, for a minimum of 5 hours!

[The Natural Philosopher]

On 21/02/2024 13:15, charles wrote:

My problem is that as currently configured the central heating comprises
mains powered thermostats all over the place and mains powered fan blown
heaters as well as the underfloor.

It's just too complex to UPS it all. Be more sense to have a 5kW diesel
genny outside in a shed...


--
Outside of a dog, a book is a man's best friend. Inside of a dog it's
too dark to read.

Groucho Marx

[The Natural Philosopher]

On 21/02/2024 13:01, Paul wrote:

I dont run RAID for that reason.

I just have mirror disks, synched once a night.

RAID is not for backup, it is for high availability.
No domestic setup needs RAID.


...

>
> RAID arrays still need backups. And a UPS helps prevent them
> from becoming de-synchronized.
>

So whats the point of RAID?
In short its not a data protection strategy at all, its high
availability to data in a data centre

> I do not really know what keeps consumer SSDs alive on power failures.

They are not kept alive.
They shut down smoothly. Probably have big capacitors to flush writes to
the NVRAM if they detect power failure. I pull the plug on mine often,
without issue.

> It's supposed to be a "firmware scheme", but since they don't have
> advanced power fail detection (and a Supercap), it's not hardware
> that protects them against critical data loss. It's hard to imagine the
> flash has sufficient life for any sort of firmware scheme to make
> the device "reliable".

You appear to be babbling.

Flash doesn't need power to retain data, It will only cache data in RAM
for a short while before writing it, and the time to write it if
external power goes down is microseconds. It doesn't need a supercap. An
ordinary one will do. And it doesn't need 'advanced power fail
detection' a simple monitor of supply voltage on the far side of a diode
will serve to tell them they have lost external power and to flush all
caches to NVRAM now.

How do you *think* SSDS would work if you shutdown the computer they are
attached to? They don't have a 'shutdown' signal. They just get the
power removed. They presumably simply DO monitor supply voltages .

[The Natural Philosopher]

On 21/02/2024 13:17, Tim Lamb wrote:

I saw the same on the Decca Elizabethan used to test radar systems.
Before takeoff there was a massive whining under the floor 'what's
that? ' 'Its our rotary converter: powers everything in the racks off
the aircraft 48V' 'Why not use transistors?' 'because when the wheels go
up we are lucky to get 24V out of the batteries: the rotary converter
has enough spinning mass to keep it all stable'



--
It is the folly of too many to mistake the echo of a London coffee-house
for the voice of the kingdom.

Jonathan Swift

[NY]

On 21/02/2024 03:26, John Rumm wrote:

The one piece of advice that I would give you, from learning the hard
way, is when you receive the UPS, bite the bullet and actually make sure
it works while it's still in warranty, and do it at a time when you can
manage without the various computers, both when you are shutting them
down cleanly to allow the UPS to be interposed between the mains and the
computers, and when you simulate a loss of mains and hope that the UPS
will work.

My wife bought an expensive PC which came with a UPS - probably rated at
700 VA since that was a common size at the time.

We didn't test it at the time, and only got round to trying it a year or
so later, by which time its manufacturer's warranty had expired. Add it
was as dead as a dodo. Even after leaving the battery on charge for a
couple of days (vastly excess of what its battery should need), it would
not supply any power.

I took it out of the PC setup and tried it in isolation. It lit a 60 W
tungsten bulb for about 5 seconds. It lit a 7 W LED bulb (Philips Hue,
IIRC) for about 15 seconds. Powered by the mains, and connected to a PC
by mains and by its USB monitoring connection, with the PC running the
UPS's monitoring software, the UPS reported the battery state as
"excellent" but the UPS would not run off that battery.

This is something I have experienced in several situations. I have a
Samsung laptop and its battery is reported by Windows and by MX Linux
(booting off different HDDs) as 100% capacity while connected to the
mains PSU/charger, but as soon as I unplug the PSU, the laptop turns off
instantaneously.

It seems that laptops and UPSes can "see" their battery as holding a
full charge, but as soon as you remove the power input, the device stops
working, as if the battery is really as flat as a pancake.

IN my experience, don't trust the UPS hardware and software to tell the
truth - test it periodically by simulating a power cut.

And simulate the type of power cut that you typically get. It may be a
long power cut or it may be a series of brief 1-second cuts in rapid
succession. My Windows 7 PC seems to be fine with a single power cut
(whether brief or several hours) and will always boot fine afterwards.
But several 1-second cuts at 10-second intervals will knacker the HDD.
Not irreparably, but enough to require a very long file-system check
before it will start to boot.

[Reentrant]

On 21/02/2024 12:00, Jeff Gaines wrote:
> On 21/02/2024 in message <ur4o0v$33uk8$2...@dont-email.me> SteveW wrote:
>
>>> I've always lived in rural areas with overhead cables so power cuts
>>> are frequent. I have it set up so as soon as mains power is lost the
>>> PC  shuts down, I don't expect it to run the PC in the event of a
>>> power cut.
>>
>> Do you actually have it set to shut the PC down immediately or with a
>> couple of minutes' delay? The latter would allow for times when the
>> power cuts out, but reconnects shortly after.
>
> The latter, hibernates after 3 minutes.
>

My NAS, PC and UPS talk to eachother via USB. Rather than setting a time
to run on battery power, I've set mine to shut down when there's 5%
charge remaining.

I only have a small UPS - the point being to let the PC and NAS shut
down gracefully avoiding any disk corruption, rather than to let me
carry on working during an extended power cut.

--
Reentrant

[John Rumm]

True RAID is not a backup strategy, but it is a layer of fault tolerance
that can save downtime. You can also get increased throughput with the
higher level RAID categories as well.

[John Rumm]

On 21/02/2024 11:49, SteveW wrote:

I have mine set to initiate shutdown when the reserve power reaches a
threshold (like 20% remaining). That still leaves some scope to power
something back up again during a power cut if it became necessary.

[Sam Plusnet]

On 21-Feb-24 3:26, John Rumm wrote:

> On 20/02/2024 20:46, Sam Plusnet wrote:
>
>> I lost a PC PSU to a couple of micro-power cuts and (no doubt the
>> associated voltage spikes etc.), so I decided to get a UPS to protect
>> things.
>>

Exactly the model (1200VA) I am contemplating - but when I placed an
order for one, the supplier insisted that Cyberpower required a signed
statement that it was to be supplied as a commercial item, and limiting
some of a retail customer's rights. They also claimed that this didn't
reduce my statutory rights - but I didn't accept that.

>
> Something else to consider when supporting multiple bits of kit is how
> you will synch the shutdown of the attached loads. Most UPS devices have
> a USB connection these days that lets you connect a single PC or other
> device and monitor it. That also allows you to specify a charge
> remaining threshold when the device should power down. That is easy with
> just one PC.

I intend to use the USB connection to do a controlled shutdown of the
NAS - that being the most vulnerable item. If the PC is running, I
should be sat in front of it, or close enough, and so able to do a
manual shutdown in plenty of time.

>
> However it gets a bit more complicated with multiple devices. There is
> an open source suite of software called NUT (Network UPS Tools), that
> allows one device physically talking to the UPS to act as a server and
> share information about the current power state with multiple clients. I
> found the Synology box actually uses this for its default UPS monitoring
> capability (although it does not seem to name it directly). That made it
> easy to get a NUT client for the main windows machine running the
> hypervisor, setup the NAS as the NUT server, and point the windows box
> at that. That the whole lot can be gracefully shutdown in sequence, and
> then finally switch off the UPS itself as well once the available
> capacity falls below the desired capacity threshold.
>
> (on restoration of mains, everything is configured to come back up can
> carry on were it left off)
>
>> I'm certainly not the first person to go down this route so...
>> Comments please.
>
> I have an extension lead made up with exposed individual wires, so that
> I can loop them through a clamp meter:
>
> https://wiki.diyfaq.org.uk/index.php/File:MainsCurrentTestLead_(Medium).jpg
>
> Makes a handy way to get a feel for the actual size of UPS required.
>

--
Sam Plusnet

[Sam Plusnet]

Thanks. That sounds like very good advice.

I've read reports of people who said their UPS claimed to be at 100%,
but then fell over in a few seconds with only a minor imposed load.
However I hadn't thought of the warranty aspect.

--
Sam Plusnet

[Sam Plusnet]

Indeed.
Choices made should reflect the expected use-case. I rarely play games
now, and the ones that I do are not going to stress a modern system too
much.
If a power cut (greater than a second or two) happens, I want the UPS to
hold up long enough for me to save files and safely power down all
systems - not to carry on playing some cutting-edge game at max settings
for the next hour or two.

>
> I originally budgeted for one PC on the UPS, but eventually
> had two on it. You would not expect too many cases where
> they would go-to-max on their own. The UPS is disconnected
> at the moment, because the battery is dead, and I did not
> like the failure mode it displayed.

That's another good point. You buy a UPS to support the setup you have
- but we all tend to change kit from time to time. It usually pays to
be generous when specifying.

--
Sam Plusnet

[Tim Streater]

On 21 Feb 2024 at 15:29:40 GMT, "NY" <m...@privacy.net> wrote:

> IN my experience, don't trust the UPS hardware and software to tell the
> truth - test it periodically by simulating a power cut.

Good advice, but we don't have to simulate them here.

--
"Freedom is sloppy. But since tyranny's the only guaranteed byproduct of those who insist on a perfect world, freedom will have to do." -- Bigby Wolf

[SteveW]

Yes. My RAID has a battery backed buffer and is very tolerant of sudden
shutdown and of course of a disk failure, it also does increase
throughput and allows a greater total capacity than mirroring. Of course
I do back up to another place.

When I first got a RAID card (same as the one I use now, but dedicated
to the server it was in, rather than a more generic PC), I set it up
with a single disk, for testing. I set it to RAID 1, but didn't fit the
second drive. All worked well, although it obviously reported a fault
with the second drive. I then fitted more drives and told it to convert
the array to RAID 5. During the night, part way through conversion, we
had a power cut. When I restarted the server, conversion continued from
the same point and completed later that day, with no problem. At all
times during the conversion, the test data remained available and
intact. I was impressed.

[Paul]

A lot of what I've learned about SATA SSDs, comes from reviews on the
Anandtech site.

They used to show pictures of controller boards. They would show the
area on the consumer PCB, where pads were available for a Supercap plus
an SMPS powered by the Supercap, but the components were not on the PCB.

Yet, on an Enterprise drive they reviewed, the Supercap and SMPS were populated.

This suggested that reliable shutdown procedures on the Enterprise drive
were established by:

1) Advanced power fail detection. Noticing that the external rail
was collapsing.
2) Operation of the Supercap plus SMPS, to continue operating the PCB.
3) Put-away of critical data. You would not go to this much trouble,
unless there was a reason to be doing this. Some SSD drives have
a DRAM cache, and some are cache-less. The cache-less ones potentially
have less writes to do at shutdown.

In the case of the Consumer drive, there is no backup power, and the
size of bypass capacitors is limited. You cannot use a too large bypass,
because if the SSD is connected to a USB bridge, the capacitance would
violate the 10uF limit on USB peripherals (the inrush concern and rail
collapse issue).

Reliable recording of the virtual to physical sector map inside
the drive, must be implemented in some other way. With no backup
power system, if a consumer SSD drive loses power, it has *no* resources
to help itself. Without a backup power source, it would have to frequently
either record or update the virtual to physical mapping table, as the table
contents changed. Without the mapping table, the information inside the
SSD drive is scrambled and unusable. Sector 0 of an SSD is not a location 0
in the flash. The sectors move around, according to wear leveling requirements.

While it has been mentioned previously, that critical data is stored
in flash devices, in an "SLC-like" small area, this isn't good enough,
because it does not have the write-life for the frequency of updates
required. The SLC-like area would be good enough, if the drive only
had to write that area once, at shutdown. How many blocks could
you write, using a 10uF cap as a power source. The answer is: not many.

It's not obvious what method is used to make consumer drives reliable.
Yes, I've had the power go off here, and mine survived. It would be
comforting to know what the method was, as a means of estimating
how reliable it might be.

As an example, someone in one of the other USENET groups, is the equivalent
of Geek Squad. He deals with consumers and SOHO/small business people.
He fixes their problems, does their updates, designs automated backup schemes.
He also sells them equipment. In particular, Samsung drives.

He's had some returns, drive failures. Well, it would be nice to know
what those customers did, to have those drive failures. I don't
know the ratio of drives sold to returned units. I've had no trouble
here, but my sample size is tiny and meaningless.

Early SSD drives were terrible. And it was an article about Intel
entering the SSD drive business, and getting their hands on the
source code of the firmware, and doing a Picard facepalm when they
saw what typical firmware was doing. So at least initially, the
firmware was flawed from an algorithm perspective. But there were
no further details, on whether they shared what they observed,
with anyone else.

Even hard drives have had algorithm failures, one of which
caused a data structure the drive relied upon, to corrupt
roughly one month after the drive started being used. You could
recover drives with that failure. It involved putting a piece
of cardboard between the head cable pads and the head cable.
Operating the drive, without the drive being able to read the
platter. Typing in two cryptic commands into the drive TTL-level
serial port. Then, pulling the cardboard away and seating the PCB.
And then your data was accessible again. Some other drive issues
have been fixed by replacement code images. That's a quality issue,
rather than a too-many-noobs issue for the industry.

Hard drives solve the power problem, by turning the motor into
generator, by modifying the H-bridge switch settings. Power
from the (generator), is used to power the voice coil and cause
the heads to retract up the ramp. but at the same time, some
"last writes" get done too. On some of the newest drives, drives
which have 512MB cache chips, the drives have been equipped
with additional flash memory on the hard drive controller board.
The flash memory receives the contents of the 512MB cache, as
the drive is doing emergency power fail procedures. This is only
on the most expensive drives. Drives with 256MB cache, the drive
seems to have the time to write the cache to the platter. And that's
an example of a "carefully budgeted" emergency procedure.

Do SSDs have a procedure they could tell us about ? I'm listening.

They're not issue-free.

https://www.techpowerup.com/forums/threads/samsung-870-evo-beware-certain-batches-prone-to-failure.291504/page-12

Paul

[Paul]

They do a battery test, once a day. A kind of impedance test.

If the battery fails the load test, the unit will beep once.

There may also be a button on the casing, that does a
"flip to battery" inverter test. It simulates loss of
mains. But even without inverter testing, it will check
the battery for you.

Modern UPS can have a tiny display on them and a CPU,
and so there is a better chance the response will be
intelligible. On my old one, it's all meant to be
mysterious.

On an SPS UPS (the lowest form), the chassis is made
of a piece of heavy steel. And it is ice cold to the
touch. If you feel the chassis, and the chassis is
a bit warm to the touch, this means cells in the lead acid
battery have failed short, and the battery has changed from
a 12V battery, to a 6V battery with three cells shorted.

By feeling the heat, that's when I knew it was time to take
it out of service.

High end ones, double conversion with sine wave output in
server rooms, those have a fan, and the inverter is running
all the time. Those are more likely to be well designed.
And do a more thorough job on test.

At work we bought more than 100 UPS in a bulk purchase,
and put them on the office computers. These were cheap SPS
(Standby Power Supply) type UPS. The failure rate off
the pallet was 10%. Some units would not flip to battery
on loss of mains. Some units would not flip off battery
when mains power returned. The nicely distributed flaw
types, suggest the units were not acceptance tested
before being shipped.

Units ship with the battery disconnected from the unit.
This might prevent some amount of self discharge. I
don't really know what the "shelf life" of a boxed UPS
is, in terms of not damaging the battery by leaving it sit.

Battery life, is all over the place. Original battery lasted
11 years (perhaps longer than what other people experience).
The battery still had full voltage (no shorted cells), but
no longer had good capacity. The battery impedance test
once a day, indicated it needed help. But it still behaved
like a 12V battery.

The replacement lasted 3 years, and the chassis got warm on
the replacement battery life cycle. Measurement with a
meter later, indicated that half the cells had failed short
and it was then a 6V battery instead of a 12V one.

Checking the float charge (operating the UPS without the
cover on it), the float was 13.5V, which is more or less
what I expected it to be. If the float wasn't right for
the replacement pack, that could lead to a short life.
But the replacement was branded, so the company should
have checked that the Chinese battery actually had the
right characteristics. Even the *original* 11 year battery
(with branding label adhered over the Chinese name),
was a Chinese one, so it's not that it is Chinese that
mattered. Something must have been wrong with the specs
of the second lot.

And there still aren't a lot of lithium based ones. If done
that way, they should be LFP (lower density, but happy go lucky).
I'm not sure the UPS companies are prepared for the liabilities
involved.

Paul