Maximum Volume Bytes for Ultrium LTO-7 tape

[Frank Cherry]

Hello there,

I'm storing on Ultrium 7 LTO tapes with a single drive unit.
It is right, to set in the pool config the  

Maximum Volume Bytes = 15000G          # Limit Volume size to something reasonable

to 15000G ? The tape is specified with 6 / 15 TB (uncompressed / compressed)

Is the tape drive works as default with compression? How can I check it and can I define it on the SD config?

Thanks, Frank

[Brock Palen]

I wouldn’t bother.  Modern LTO drives (any made in lay 10 years) auto detect end of volume. I do t use this setting at all with my two drives and it auto sorts it out. 

This is important because the 15T quoted assumes compression of a given ratio. That can very drastically. If you use client side compression you won’t see any compression at all. Similar if most your data are video and doesn’t compress well. If it’s all text emails you will get more than listed. 

Let the drive auto detect and it will work the best. I think this is one of the things you can test with the btape command. Highly recommend you run all the tests in btape abd make sure they pass. 

I only use max volume size with disk volumes.

Sent from my iPhone

Brock Palen

989-277-6075

On Dec 25, 2020, at 12:38 PM, 'Frank Cherry' via bareos-users <bareos...@googlegroups.com> wrote:



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[Brock Palen]

Also compression look up the mt commands. But most are on by default. Only encryption is anything you need to mess with in bareos. Again if doing client compression you won’t see much if any on the tape side. If your not you should see it. 

You can verify how much compression your getting two ways. One is the volume size bareos reports being larger than the 6T native size. 

The other is look at the sg_* commands. One will read ann the drive and currently loaded tape data. One will tell you compression ratio read / written for the tape. 

Sent from my iPhone

Brock Palen

989-277-6075

On Dec 25, 2020, at 12:53 PM, Brock Palen <bro...@mlds-networks.com> wrote:

I wouldn’t bother.  Modern LTO drives (any made in lay 10 years) auto detect end of volume. I do t use this setting at all with my two drives and it auto sorts it out. 

[Brock Palen]

Found the command it’s

sg_logs -a <device>
sg_logs -a /dev/sg5

<lots of data>
Data compression page (LTO-5 specific) [0x32]
Read compression ratio x100: 109
Write compression ratio x100: 100


You can see I’m not compressing at all because I’m doing client side compression (backing up over home networks)

You can also compare the bareos volume size to

Tape capacity page (LTO-5 and LTO-6 specific) [0x31]
Main partition remaining capacity (in MiB): 46592
Alternate partition remaining capacity (in MiB): 0
Main partition maximum capacity (in MiB): 800226
Alternate partition maximum capacity (in MiB): 0

Which is the native capacity, if your volume is larger than your actual consumed your compression is working.

Brock Palen
bro...@mlds-networks.com
www.mlds-networks.com
Websites, Linux, Hosting, Joomla, Consulting

[Frank Cherry]

Thanks for the information, I will play with some test backups and see, also install sg_utils and check.

Thanks a lot, Frank

[DUCARROZ Birgit]

Hi,

That's right, don't use any Maximum Volume Bytes. All my LTO-7 tapes are
a bit different, sometimes it backupe's 6T, sometimes 8.5T.

If you need some config files, let me know.
Regards,
Birgit

> www.mlds-networks.com <http://www.mlds-networks.com>

> Websites, Linux, Hosting, Joomla, Consulting
>
>
>
> > On Dec 25, 2020, at 12:58 PM, Brock Palen
> <bro...@mlds-networks.com> wrote:
> >
> > Also compression look up the mt commands. But most are on by
> default. Only encryption is anything you need to mess with in
> bareos. Again if doing client compression you won’t see much if any
> on the tape side. If your not you should see it.
> >
> > You can verify how much compression your getting two ways. One is
> the volume size bareos reports being larger than the 6T native size.
> >
> > The other is look at the sg_* commands. One will read ann the
> drive and currently loaded tape data. One will tell you compression
> ratio read / written for the tape.
> >
> > Sent from my iPhone
> > Brock Palen

> > 989-277-6075 <tel:(989)%20277-6075>

> >
> >> On Dec 25, 2020, at 12:53 PM, Brock Palen
> <bro...@mlds-networks.com> wrote:
> >>
> >> I wouldn’t bother. Modern LTO drives (any made in lay 10 years)
> auto detect end of volume. I do t use this setting at all with my
> two drives and it auto sorts it out.
> >>
> >> This is important because the 15T quoted assumes compression of
> a given ratio. That can very drastically. If you use client side
> compression you won’t see any compression at all. Similar if most
> your data are video and doesn’t compress well. If it’s all text
> emails you will get more than listed.
> >>
> >> Let the drive auto detect and it will work the best. I think
> this is one of the things you can test with the btape command.
> Highly recommend you run all the tests in btape abd make sure they
> pass.
> >>
> >> I only use max volume size with disk volumes.
> >>
> >> Sent from my iPhone
> >> Brock Palen

> >> 989-277-6075 <tel:(989)%20277-6075>

> >>
> >>> On Dec 25, 2020, at 12:38 PM, 'Frank Cherry' via bareos-users
> <bareos...@googlegroups.com> wrote:
> >>>
> >>> 
> >>> Hello there,
> >>>
> >>> I'm storing on Ultrium 7 LTO tapes with a single drive unit.
> >>> It is right, to set in the pool config the
> >>>
> >>> Maximum Volume Bytes = 15000G # Limit Volume size to something
> reasonable
> >>>
> >>> to 15000G ? The tape is specified with 6 / 15 TB (uncompressed
> / compressed)
> >>>
> >>> Is the tape drive works as default with compression? How can I
> check it and can I define it on the SD config?
> >>>
> >>> Thanks, Frank
> >>>
> >>> --
> >>> You received this message because you are subscribed to the
> Google Groups "bareos-users" group.
> >>> To unsubscribe from this group and stop receiving emails from
> it, send an email to bareos-users...@googlegroups.com.
> >>> To view this discussion on the web visit
> https://groups.google.com/d/msgid/bareos-users/f7fef681-396f-47dc-8a76-6a28547e7caan%40googlegroups.com

> <https://groups.google.com/d/msgid/bareos-users/f7fef681-396f-47dc-8a76-6a28547e7caan%40googlegroups.com>.

>
>
> --
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