SDLT 220 Drive Speed Problems

[koltes]

Hello,

I've got a problem with an external SDLT 220 drive attached to an Adaptec AHA-3944AUWD controller (HVD) with an interface troughput of 40 MB/s. However, even if highly compressible data is sent to the drive the maximum speed reachable is slightly less than 25 MB/s. The drive writes data for about 2 seconds, stops, waits for new data for about 5 seconds and restarts writing for another 2 seconds...

Are the internal interfaces of the drive not capable of handling more data per second or is this a problem on the computer side (data source is a RAID 5 system with 4 hard drives so that shouldn't be the problem)?

Best regards,

Andreas Koltes

 

[adpwl1]

Well the SDLT220 are rated for 11MB/sec so at a 2:1 compression you need to plan for 22MB/sec. Your SCSI card is rated for 40MB/sec, so you should be good.

Now there are a lot of other factors to look at when doing tape backup.
Is the raid set fragmented?
What is the internal bandwidth of the server?
Is the data local or on the network?
What is the backup software?
Does this SCSI card sit on the same PCI bus as the RAID system?

Theser are just a few.

 

[anawrocki]

I would suggest testing it with say a single large file versus many small files and look at the restult. I have a simular setup/issue where a 24 GB SQL Dump will get backed up at 1.2 GB a minute from a dedicated volume, while a typical large volume of file and print data on the very same server will hover around 100MB a min and CPUs spike. Look at your backup options as well (what are you doing with the archive bit and how are you verifying the backup).

 

[bigjim968]

Defragment your disks ;-)

I observed that the performances changed MUCH afterwards.