Amanda backup on PX502 with HP 960 LTO-3.

[Kumsup Lee]

I am using amanda-2.5 for backup. When I run "amtapetype", it generate.

define tapetype HP-LTO3 {
comment "HP Ultrium 3"
length 386048 mbytes
filemark 0 kbytes
speed 1407 kps
}

How can I diable H/W compression from ltt ?

Thanks,

Kumsup Lee

[Richard Bickers]

To answer your question, you can run the Set Device Configuration test using the options to set/unset data compression.

However, it is advisable to leave data compression on with these drives as it's done in hardware, gives you greater capacity and potenitally higher transfer rates.

Our advice is to turn off any software compression done by the application as that will slow your backups significantly.

I don't know anything about Amanda backup so I'm not sure what the output is telling you. Is that 1.4 MB/S?!

You can use LTT to find out how fast your system can write data to the tape drive using the Device Performance test. This will write data to tape without the application and measure the performance so you can find out if your HBA and cabling is constraining performance. You'll probably find it's a great deal faster than 1.4 MB/S.

Most likely it is the disk IO which is the bottleneck which you can also measure with LTT. Use the System performance backup pre-test to measure how fast your system can source the backup data.

Do make sure your HBA is supported, your cables are good (U320 remember) and connected properly and you're using the auto termination of the drive if external or correct termination if internal. Also make sure the tape drive is the only device on the bus - anything else will affect the speed negotiation.

Hope this helps, Richard. (LTT team).

[Kumsup Lee]

I am using:

Dual Opteron 248

-bash-3.00$ cat /etc/redhat-release
CentOS release 4.4 (Final)
-bash-3.00$ uname -a
Linux ***.***.***.*** 2.6.9-42.0.2.ELsmp #1 SMP Wed Aug 23 13:38:27 BST 2006 x86_64 x86_64 x86_64 GNU/Linux
-bash-3.00$

I am using ltt-4.1. But I couldn't find "Device Configuration test" from "picktest". It has "Drive Configuration test". It has one option for password.

---- Some output from ltt-4.1 ----

Main > Drive Information > Device Performance Tool > Viewer >
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Opening Tape Drive 20.1.0[2-/dev/sg9]
Successfully opened the Tape Drive /dev/nst0
0 MB written in 23.8289 seconds at 0.0000 MB/s
0 MB read in 20.0206 seconds at 0.0000 MB/s
Device performance tool has successfully completed execution.
Opening Tape Drive 20.1.0[2-/dev/sg9]
Successfully opened the Tape Drive /dev/nst0
0 MB written in 25.6722 seconds at 0.0000 MB/s
Device performance tool has successfully completed execution.

Main > System Performance Tools > Backup Pre-Test > Viewer >
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
807.414174 MB read (5081 files) in 25.212402 seconds with rate 32.024484 MB/sec
Backup Pre-Test successfully read files.

Main > System Performance Tools > Restore Pre-Test > Viewer >
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
1020 KB written (8 files)
Restore Pre-Test successfully created files.

Thanks,

[Richard Bickers]

Sorry, yes, you're right, it's 'Drive' configuration test.

To change the options in that test type 'testoptions' after you've picked the test. You should find what you need to turn DC on/off in there.

Having said that, DC is not your issue.

The performance tests you ran showed that your disk IO is good for reading at 32 MB/S but your drive IO is running at < 1 MB/S (sorry - there's a bug in LTT 4.1 than turns this into 0 MB/S [fixed in 4.2]) which is dire. That's where your problem is.

Please check the type, termination and conditions of your cable. Make sure the HBA is supported and up to date and that the drive is the only thing on the bus. Is this an internal drive? Power cycle the system to make sure the SCSI speeds are re-negotiated.

You can also pull a support ticket using LTT and look at the drive->health->device analysis to see if it is picking up on any SCSI communication errors, bad configurations etc. Let me know if you need any help interpreting the ticket - there's quite a bit of useful info in there.

Good luck, Richard.

[Richard Bickers]

Another thought - it turns out there's another reason that the device performance test might give you zero with 4.1 so please try this:

Set option #4, "Set the no. of blocks per read/write to tape (count)" to 32. This will ensure that each write transfer has enough data to be counted so the sum doesn't end up at zero.

This will be fixed in 4.2 (November) and is also not and an issue in the previous release (4.0 SR2) which is still available on hp.com.

Please try using this changed parameter and see what your drive performance rates show.

Richard.