On Wed, 14 Apr 2004, N.J.Tustain wrote:

>I noticed a strange reduction in backup rate, anyone got any idea's:
>
>I have four sessions backing up to one drive (AIT3) with a resonable
>backup rate, I've seen between 10MB/S and 24MB/s. When a fifth session
>starts backing up to a second AIT3 drive the total backup rate drops to
>approx 3MB/s total for both drives.
>
>I don't imagine this is a bottleneck with the server or SCSI card etc.
>
>The jukebox has four drives in it and it appears to happen across any
>two drives. At present they are all on the same SCSI channel. Networker
>issue ?, it's version 7.0.

Does the problem happen with any client? You can take several steps in
an effort to track down the source of the delay.

Start with your server. Take a large file that's on your backup server
and copy it directly to tape, using a scratch tape. Do not use NetWorker.
Do this for each tape device. On Unix, you can do something like

  timer cp large_file /dev/whatever

If you see no delays there, try copying that same large file from
your server to each client via ftp and see how long that takes.

Another source of the delay may be that your clients are under a
heavier load than they have previously been during your backup period.

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