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MSA 1500 slow performance

 
CA1270376
Occasional Visitor

MSA 1500 slow performance

I have a msa 1500 with 3 enclosures. They have the latest firmware. I am currently getting about 8-12m/s throughput during my tape backups using a LTO 460 scsi connected to a DL380 G4. I am told the 460 max is 60m/s. The disks are highly fragmented. I've talked to tech support and in the end they were unable to help me. The tech concluded that it was a performance issue with the scsi mirrored drives on the dl380 because doing a sys perf with library tape tools it showed a write test of 9m/s, which he said is super slow. I ran the server performance advisor and it says system is normal. Can anyone help me please.
5 REPLIES 5
CA1270376
Occasional Visitor

Re: MSA 1500 slow performance

Sorry I forgot to mention that I am using 250GB SATA drives
Uwe Zessin
Honored Contributor

Re: MSA 1500 slow performance

Highly fragmented files means that you have lots of small segments on the disk that need to be picked up by the backup. These segments will have to be located first by going to the file system meta data. This means that the backup will be slowed down due to a lot of seek operations.

A tape drive can easily achive a steady data stream, because it just have to move forward. A disk has to move its head assembly and then wait until the right sector(s) pass the read head. Combine this with higher seek times on SATA disk drives (the smaller cost has to be _somewhere_) and it should be clear why your performance is that low.
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CA1270376
Occasional Visitor

Re: MSA 1500 slow performance

What kind of speeds should I be getting on the 460 with the configuration that I have?
Uwe Zessin
Honored Contributor

Re: MSA 1500 slow performance

I am sorry, but I don't think that _anyone_ can predict a value based in this numbers.

I would first see if defragmenting the disks can speed up your backup enough (what software are you using?). Again, I don't think anyone can predict how fast it will go after defragmenting, because it depends on so many factors.

The 60 Megabyte/second number on the LTO 460, by the way, assumes that your data is compressable by a 1:2 factor and that you are using Ultirum 2 media. The tape drive can 'slow down' its speed (it's called data rate matching) between 10 and 30 MegaByte/second.

From your numbers it looks like your tape goes into a start/stop mode from time to time. It is also called 'shoe-shining', because the tape must move a bit back and then go forward again, so that it continues writing at the correct tape spot. I think it is obvious that this causes additional wear on the tape drive and media and slows down your backup further.
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CA1270376
Occasional Visitor

Re: MSA 1500 slow performance

I am using commvault galaxy for backup. It is already compressed data. And I am using LTO 2 media. If there is no bench mark on speed then how do I determine if I am getting speeds that are the best that I can get?