Slow iSCSI tape performance

[david.p...@perdrix.co.uk]

I've seen a report that disabling Test Unit Ready across the iSCSI link can hugely improve performance of remote tape drives.

Is this something I do at the machine hosting the tape drive or at the client?

Is it relevant to open iscsi?

Thanks

David

[The Lee-Man]

I haven't heard about disabling TUR for iSCSI tape improvement. Even if true, I'm not sure how you'd do that. You'd need to modify your target IMHO to always reply "ready" for TUR. But TUR is used to clear some conditions at the target, if present, so not sure about the semantics of ignoring TURs. Have you tried setting the streaming bit for the tape drive?

[David C. Partridge]

I believe that it’s something to do with stopping Windows (at the target) from sending TURs to the tape every 30s or so.

 

Setting streaming bit ? Is that something I can do with mt-st or mt commands?  The best I am getting is about 29MB/s over a 1Gbit LAN L

 

Here’s my backup script:

root@charon:~/bin# cat backup-system

#!/bin/bash

# init

 

function pause(){

   read -p "$*"

}

 

#

# Connect to the iSCSI tape drive and make sure it's set up

#

sudo iscsiadm -m node --targetname "iqn.2008-08.com.starwindsoftware:mercury-hp1840" --portal "192.168.129.66:3260" --login

sleep 5

sudo stinit -vv

 

# Set the device blocksize to 64k

set -v

sudo mt-st -f /dev/st0l setblk 65536

 

#

# Actually run the backup

#

sudo dd bs=16M if=/dev/disk/by-id/ata-KINGSTON_SVP100S296G_312Y10B7Y5SK | pv | dd ibs=16M obs=64K of=/dev/st0l

set +v

pause 'Press [Enter] key to unload the tape ...'

sudo mt-st -f /dev/st0l offline

sudo iscsiadm -m node --targetname "iqn.2008-08.com.starwindsoftware:mercury-hp1840" --portal "192.168.129.66:3260" --logout

root@charon:~/

Thanks

--
You received this message because you are subscribed to a topic in the Google Groups "open-iscsi" group.
To unsubscribe from this topic, visit https://groups.google.com/d/topic/open-iscsi/jp7zMTdWbN8/unsubscribe.
To unsubscribe from this group and all its topics, send an email to open-iscsi+...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/open-iscsi/4ad354c3-5d6a-4b1f-b978-afee5d1219aen%40googlegroups.com.

[Ulrich Windl]

>>> The Lee-Man <leeman...@gmail.com> schrieb am 25.10.2020 um 17:51 in
Nachricht <4ad354c3-5d6a-4b1f...@googlegroups.com>:

> I haven't heard about disabling TUR for iSCSI tape improvement. Even if
> true, I'm not sure how you'd do that. You'd need to modify your target IMHO
> to always reply "ready" for TUR. But TUR is used to clear some conditions
> at the target, if present, so not sure about the semantics of ignoring
> TURs. Have you tried setting the streaming bit for the tape drive?
>
> On Wednesday, October 21, 2020 at 6:43:22 AM UTC-7 david.p...@perdrix.co.uk
> wrote:
>
>> I've seen a report that disabling Test Unit Ready across the iSCSI link
>> can hugely improve performance of remote tape drives.

Bit isn't it as slow _with_ iSCSI as it is _without_? My guess is that a TUR in the middle of a tape rewind will respond after the current command has completed.

>>
>> Is this something I do at the machine hosting the tape drive or at the
>> client?
>>
>> Is it relevant to open iscsi?
>>
>> Thanks
>> David
>>
>

> --
> You received this message because you are subscribed to the Google Groups
> "open-iscsi" group.
> To unsubscribe from this group and stop receiving emails from it, send an

[Lee Duncan]

On Oct 25, 2020, at 10:42 AM, David C. Partridge <david.p...@perdrix.co.uk> wrote:

I believe that it’s something to do with stopping Windows (at the target) from sending TURs to the tape every 30s or so.

Okay, that makes sense. But that has nothing to do with open-iscsi, or even iSCSI at all.

 

Setting streaming bit ? Is that something I can do with mt-st or mt commands?  The best I am getting is about 29MB/s over a 1Gbit LAN L

I was talking about the ability to tell st to write tape marks without waiting. This is very handy for streaming tape drives, since it allows it to stream tape marks as well. But it cannot be set with “mt” — it needs an ioctl().

What kind of throughput does the tape drive supply directly?

 

Here’s my backup script:

...

[David C. Partridge]

Direct throughput about 140MB/s

 

From: open-...@googlegroups.com [mailto:open-...@googlegroups.com] On Behalf Of Lee Duncan
Sent: 26 October 2020 22:51
To: open-iscsi
Subject: Re: Slow iSCSI tape performance

 

On Oct 25, 2020, at 10:42 AM, David C. Partridge <david.p...@perdrix.co.uk> wrote:

--

You received this message because you are subscribed to a topic in the Google Groups "open-iscsi" group.
To unsubscribe from this topic, visit https://groups.google.com/d/topic/open-iscsi/jp7zMTdWbN8/unsubscribe.
To unsubscribe from this group and all its topics, send an email to open-iscsi+...@googlegroups.com.

To view this discussion on the web visit https://groups.google.com/d/msgid/open-iscsi/CCD69511-2C68-4703-9BDD-A1345922DA2D%40gmail.com.