Hardware compression problem with 12.5 and HP ultrium 920

[mbrowndcm]

Hello,

There is a problem that appears to be related to hardware compression, as the "throughput" of the job (the MB/sec) seems to be cut in half from ~800MB/sec to ~400MB/sec.

This has been occuring for several months (as reported by the site).

I have found an interesting article on using the tracer.exe tool to identify if the tape drive is being set to full compression: http://www.symantec.com/business/support/index?page=content&id=TECH50960

When I trace the conversation between backup exec and the tape drive the following results are found:

--Backup exec job tracer.exe log:--

MODE_SELECT6 (sends commands to hardware)

Data byte 5: 0F = Data Compression Page is being modified

Data byte 7: C0 = Data Compression is being turned on

MODE_SENSE6 (response from hardware)

Data byte 5: 44 = not good

Data byte 7: 00 = Data Compression is being turned off

MODE_SELECT6 is sending the proper command, but MODE_SENSE6 is returning that a value indicating that hardware compression is off.

In effort to fully understand, I have obtained the HP Tape Tools and performed a test called "Data Compression Test."  This tests performs a write test of 1200MB and calculates the compression ratio provided by hardware compression.

When I trace the conversation, I see the same results:

--HP Tape Tools Data compression test tracer.exe log:--

MODE_SELECT6 (sends commands to hardware)

Data byte 5: 44 = not good

Data byte 7: 00 = Data Compression is being turned off

MODE_SENSE6 (response from hardware)

Data byte 5: 44 = not good

Data byte 7: 00 = Data Compression is being turned off

The "strange" issue with this is that HP Tape Tools reports that the hardware data compression works, at a ratio of 2.62:1.

Other than enabling software compression, is there any further ideas any one has on how to troubleshoot a hardware compression issue?

Thanks,

Matt Brown

[ZeRoC00L]

are you using the Backup Exec Device drivers ?

Is the data being backuped from the local (backup exec) server or a remote server ?

Because if the data has to be copied over the network and it cannot be delivered fast enought your speed will never be the same as the HP LTT. HP LTT generates it's own data to backup so it is always streaming at maximum speed.

[mbrowndcm]

Self,

HP said to perform the following with tape tools to manually flash the latest firmware and switch on the hardware compression

1. Stop Backup exec services ("..\Program Files\Symantec\Backup Exec\ServicesMgr.exe")
2. Open HP StorageWorks Library and Tape Tools
3. Select Hardware Scan then continue
4. On the By Product tab, select the tape device under Drives
5. Click the Firmware button on the toolbar
6. On Local Firmware Files, blick Get Firmware From Web...
7. Click OK to scan for devices (this will only scan the external adapter addresses, not an internal SCSI, or other HBAs)
8. Download the latest firmware and close the download window
9. Click By Product tab, and select teh tape device under Drives
10. Firmware> Update firmware> Start Update... takes about 5-10 minutes
11. Click Utility on tool bar
12. In the Utility Group drop down, select Drive Configuration Utility
13. Click options
14. Double-click Enable/Disable Data Compression
15. Select enabled and click OK
16. Click Start Utility
17. Click OK on test results confirmation
18. Look at Operations Log for "Test Passed."
19. Close HP StorageWorks Library and Tape Tools
20. Start all Backup Exec Services
21. Test a job
     

In addition to the above tracer.exe trace, you may want to look into sgmon: http://www.symantec.com/business/support/index?page=content&id=TECH50766

[mbrowndcm]

Yes, I just changed these drivers last night.  Before (after a proliant support pack install), the Symantec drivers weren't being used, but HP's.

Thanks!

Matt

[pkh]

Why do you say that hardware compression slows down your throughput?  Are the figures quoted obtained when you have turned hardware compression off and on respectively?  Could there be some other reason for the slowdown?

Other than the hardware compression angle, you might want to look at tuning your tape drive buffers.  See my article below.

https://www-secure.symantec.com/connect/articles/tuning-my-lto4-tape-drive

[mbrowndcm]

Thanks.  I'll look into this later, but for now, it appears that the throughput of "data" stored on the tape (as in how many MB/sec of data the tape can write) is half of that of another machine with the same exact hardware and driver configuration.

However, I estimate that due to my findings, there is a problem with the signalling, and that it isn't a buffer "issue" that a tweak can fix.  However... the more performance the better!