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Re: LTO speed problems

 
PSanderson
Advisor

LTO speed problems

Hi I have an LTO 460 on a XP pro box with a raid5. The drive is connected via a 29160 and is displayed at boot time as connected at 160.

I cannot achieve better than about 12GB/hr transfer rate on the drive. I have tried the StorageWorks Tape Tools perfomance test and achive the same poor performance. I also receive the same performance when reading from the tape and discarding the output. So it is not the hard disks that are the bottleneck.

The health tab in Tape Tools says that current configuration is narrow and the recommended is wide

Is narrow likely to be enough to limit the performance?
20 REPLIES 20
PSanderson
Advisor

Re: LTO speed problems

Update

I have now tried three different U320 cables and a 39160...

I am just building a new machine to test this on.

Any ideas anyone
PSanderson
Advisor

Re: LTO speed problems

Further update

I have now tried tow totally different machines Both spec end P4's one with 1GB memory the other with 4 (both running XP Pro)

Two Ultrium 460's with the latest firmware

a 29160LP and a 39160

3 different SCSI cables

I have run out of things to try

Any suggestions very gratefully received.
Frank Van Riet
Advisor

Re: LTO speed problems

Hello,

there is some info missing in here :

- You say you are using a RAID 5 setup. How many disks? What interface ? What is the disk rpm speed?
- Do you use a RAID controller or is it software RAID...software raid is painfully slow...
- Backup speed also depends a lot on what you try to backup: a lot of small files (eg. a windows system directory) is a lot slower than a few big files (eg. movies, etc). Have you tried both ?
- what application are you using for backup?

An LTO 960 was built to be used in a large backup environment, with multiple servers sending backup streams to the tape at once..

Test that have been performed show that it is mostly the servers + disk combinations that are the real botllenecks, not the tape drive..

Regards,

Frank Van Riet
PM StorageWorks
HP Belgium
PSanderson
Advisor

Re: LTO speed problems

Thanks for responding Frank

The RAID is a sata raid 0 with 2 x 7200rpm disks. But this is a bit of a red herring as L&TT fail on the storage performance test which DOES NOT access the disk.

Also the drive is a 460.

Cheers
Paul
PSanderson
Advisor

Re: LTO speed problems

Some further info

The L&TT health check reports this

version: V31.11.2005
Firmware rev F5CD is up-to-date for Ultrium 2-SCSI as of Thu Sep 2 19:00:00 2004.
Rule 19:
The current SCSI configuration is likely to be limiting the performance of the drive.
Please check that your HBA is the correct type for the drive and that the cabling is good.
The SCSI configuration referenced is the one for which device analysis was run and/or the support ticket was pulled.
If this is not via your backup server then you may not have an issue.
Current SCSI configuration: narrow Recommended: wide
The drives hardware compression algorithm is currently switched off.
This was probably set by the backup software.
The drive's setup has not been altered.
Current SCSI transfer rate limited to: n/a Recommended: 160 MB/sec. or better
There were 19 rules checked.
Device Analysis completed, and warnings have been reported.

Although it says I have a narrow connection I am connecting to a 29160LP or a 39160 and both get the same message. The drive is the only device on the bus and there is not termination on the drive - i.e. I am using the drives active termination (the light is on)

Cheers
Richard Bickers
Trusted Contributor

Re: LTO speed problems

12GB/hr is 3.3MB/S - which is about 10% of what you should be getting. Ouch. Interesting that LTT shows the same performance so the bottleneck must be in the Server, HBA, driver, cabling, drive pipeline. Sounds like you're using the right kind of HBAs and cables and you mention high-spec servers. You've even tried multiple drives. Are you using latest drivers?

The narrow bus will limit the burst rate to 80MB/S which isn't recommended for the Ultrium 460 but that wouldn't drop your rate down to 3!

There are a few things to check on the system like IRQ assignments and making sure the drive is the only device on the bus - including switched off devices as they affect the negotiation. What is the negotiated rate from the health tab?

There's a more complete list of things to try at www.hp.com/support/pat. The focus is on the disks as that's where the bottleneck usually is but there's a few tips from the server standpoint.

This is very unusual. It's a very significant bottleneck and it's common throughout every combination you've tried.

I doubt it's the drive. If these drives do suffer error rate issues then the performance can drop by 10-20% - not the 90% that you're seeing. It sounds like a SCSI burst rate negotiation thing - as if it's negotiated to 5MB/S burst which is the lowest possible.

One thing to try/confirm is that you get the same data rate for different compression ratios which you can do from the Device Performance test in LTT. That would verify for sure that the bottleneck is not from the mechanical/physical/media part of the drive.

B.t.w. we're in the process of releasing the next update to LTT - 4.0 SR2 - which has slightly improved health output. Main difference is the performance estimates are more accurate for the previous tapes. If you write to the drive for a few minutes and then unload the tape you'll find a good estimate of the performance - which will no doubt tie up with what you've found so far... You should find 4.0 SR2 on the web site sometime next week.
It's more interesting when it's gone wrong
PSanderson
Advisor

Re: LTO speed problems

Thanks Richard

I will have another look at that link and revisit the IRQ's.

The throughput is the same for different compression rations, I have tried 1.6, 2 and 3:1 all give 3MB/s

I don't understand the narrow issue though - are either the 29160LP or the 39160 narrow. Both are rated at 160MB/s which is what I see in the adapter BIOS scan

Interesting - On the health tab under "Drive Configuration|Interface" the SCSI host ID is listed as unknown

also Drive "Configuration|Interface|Negotiated Burst Data Rate" has unknown for DT mode, bus width, clock rate and disconnect privelages - is this right?
Richard Bickers
Trusted Contributor

Re: LTO speed problems

Yes, that's odd. Seems like you're getting 160 with a 160 HBA. The device analysis rules will trigger because we recommend 320 for the LTO 3 but this is way off the scale compared with 3 MB/S!

Also odd that you're getting unknowns in the health/drive/config tab. If you can do it today (I'm away next week) perhaps you could try a device performance write to the drive, unload the tape, pull and email the ticket to the ltt_team@hp.com mailbox so we can take a look.

It's more interesting when it's gone wrong
PSanderson
Advisor

Re: LTO speed problems

Richard I am running the test now - I am interested in why you wish me to unload the tape at the end though - just curious.