Backup performance on MSL5026S2 and an Tru64 ES45

[Monica Peck]

We have a Tru64 ES45 server directly connected to an MSL5026S2 tape drive with two SDLT320 drives in it running the CommVault Galaxy (current revision) agent for backup and are experiencing backup performance probles.

Question 1) What could be causing the poor performance?
- The data is made up of 1.5TB of very large, very compressable Oracle agents.
- Oracle is being backed up offline.
- This backup takes 11.5 hours to complete a full plus another 3 hours to scan for a total of 14.5 hours. Performance when this was sent as 1 job to 1 drive was 140GB / hour.
- The job was then split into two separate jobs and writen to two drives, but the performance dropped to 100GB/hour.
- all hardware and software is up to the current revisions

Question 2 - How come the descrepancy in performance?
A test backup job of 35GB was created for troubleshooting perposes. The first time the test ran, the performance was 70GB / hour; the second time the exact same test was run in the exact same envionment, the performance was 98GB / hour. How come the descrepancy in performance in this test envioronment

[Monica Peck]

Hi,

I have a correction to the setup in our environment. The MSL5026S2 tape library is Fibre attached and connected to a DS-KGPSA-EA Fibre HBA (FCA2384); the library is NOT direct attached. CommVault is also running the SAN agent on the Tru64 server.

Thank you.

[rich pattison]

Hi

It sounds like you have a disk bottleneck. The fact that with one tape drive you got 140GB (Max uncompressed performance for a SDLT2 is less than 60GB/hr) means it was "flat-out" streaming as fast as it could go. When you split the job across two tape drives the speed of data from the disk could not keep both drives streaming, hence the performance reduction. The more compressable the data - the harder the disk has to work to keep up with the tape drive.

This could also be affecting you test results. Contention, or variable disk performance could mean the tape drive doesn't stream efficiently. The L&TT (Library and Tape Tools) software, is available as a free download from HP, and now includes tests to determine disk "feed" speed (Backup pre-test), and tape drive performance checks.

Rich

[rich pattison]

........Sorry - just remembered you are TRU64 - I'm not sure these tools are included in the L&TT UNIX package. But there are standalone tools available - PAT (performance assesment tool) for feed-speed measurement. Here's a link which talks about tape backup performance, with embedded links to the locations for downloading these tools:

http://h20000.www2.hp.com/bizsupport/TechSupport/Document.jsp?objectID=lpg50460&locale=en_US

regards