Networker

Re: [Networker] Calculating optimal paralelism and target session values

2004-01-20 02:23:33
Subject: Re: [Networker] Calculating optimal paralelism and target session values
From: "Tarjei T. Jensen" <tarjei.jensen AT AKERKVAERNER DOT COM>
To: NETWORKER AT LISTMAIL.TEMPLE DOT EDU
Date: Tue, 20 Jan 2004 02:23:44 -0500
Alexandre Dery wrote:
>The new one has 6 DLT-4000 tapes (old, I know) on a dedicated SCSI card,
>running on a HP DL380.
>
>I have some 25 servers to backup and I want to know how to calculate the
>optimal parallelism values and tape target sessions.

Make sure that you use client side compression and not hardware
compression. Otherwise you are likely to starve the DLT4000. Its
compression is so effective, that it can run out of data to write to tape.

If you have 6 drives on a single scsi bus, that is perhaps a bit much. I
would suggest that that you split these with 3 drives on each bus.

If you are worried about throughput, you could try to back up to disk or
use a (separate) staging disk.

With regards to parallelism and target sessions, we rely on trial and
error. We only use DLT4000 in single drive configuration. Our jukebox have
4 DLT7000. We used to have four sessions per drive, four drives, and a
paralellism of 16. Now we have two sessions per drive and kept the
paralellism. We also use groups to divide the clients. Clients with a lot
of disk is started first and then we fill up with the rest.

greetings,

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