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Does anyone know a way, (other than using SystemTap + iostat-scsi.stp script), to get Tape Drive performance statistics?

Server: Red Hat Enterprise Linux Server release 5.7 (Tikanga) Kernel 2.6.18-274.12.1.el5 on an x86_64

Attached Tape Devices: Number model SN HBA SCSI FO Path 0 ULT3580-HH5 1068028623 qla2xxx 1:0:0:0 NA 1 ULT3580-HH5 1068030139 qla2xxx 2:0:0:0 NA

I want to get throughput information out of these tape drives.

In AIX, you can just do iostat -p and get that information (assuming atape driver is installed). There doesn't seem to be anything like that for Linux.

Anyone know of anything?

(I don't use SystemTap + iostat-scsi.stp script because it's not meant for production. It's known to cause kernel dumps and crash systems.)

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3 Answers 3

If you're backing up from local drives, simply monitoring your disk throughput with iostat will give you a good approximation of your tape throughput (most/all of what is read from disk is going to tape).

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Test a representative set of backup data and time it. Run a tool like nmon during backup and monitor transfer speed live. Your tape drive's performance if going to depend heavily on your interconnect, disk speed, compression settings and the actual data set.

However, for HP tape devices, there's a Library and Tape Tools package that can perform tape drive throughput testing. I'm not certain if it works with non HP drives, but it's worth a try.

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Set up some test suite to get this information. Use dd with various data sizes and block sizes. Use data sources of /dev/zero, /dev/urandom (to allow for tape compression and to try to avoid tape compression). Create big files filled with /dev/zero and /dev/urandom. Copy production file systems and use dd to push the file system device to tape. Push a tar of a production file system to tape. Copy all files from a file system to tape. Copy database files to tape. Perform all these test with tape drives mounted and unmounted. Time each command or batch script.

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I just read the question again and I think you want actual production stats. I don't know enough about Linux tape to help there. –  leancz Jan 18 '12 at 12:02

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