Networker

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

2004-01-19 15:59:00
Subject: Re: [Networker] Calculating optimal paralelism and target session values
From: Darren Dunham <ddunham AT TAOS DOT COM>
To: NETWORKER AT LISTMAIL.TEMPLE DOT EDU
Date: Mon, 19 Jan 2004 12:58:53 -0800
> Hi gurus,
>
> I'm installing a new Networker 7.1 server to replace 2 other aging
> Networker servers.
>
> 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.
>
> I guess it comes down to how much target sessions my DLT-4000 can support
> at one time ?

Not only that, but how much your network, your clients, and your server
will support also.

A DLT-4000 should be able to handle something like 2MB/s raw and
4MB/s compressed, yes?  That's far less than one maxed out 100Mb/s link.

What type of network connectivity does your backup server have to the
clients?

If you have fast clients and 100Mb/s connections, then I'd probably only
start with a parallelism of 6 and target sessions of 1 on all drives.
The idea is that you want the drives to be (just barely) the bottleneck.

If you have 10Mb/s client connections or really old, slow clients, and
you've got sufficient bandwidth to the server itself (multiple 100mb/s
or gigabit), then you might bump things up a bit.  Monitor your
sessions.  If you're consistently getting slow throughput on the drives,
try bumping up one or two of the drives to target session 2.  If that
improves things, set them all to 2 and double the parallelism.

If your server itself is tight on connectivity (one single 100Mb/s
link), then you can't drive too many sessions or you'll bottleneck on
the network interface.  You can't saturate even 3 or 4 drives with a
single 100Mb/s, so increasing parallelism wouldn't help anything.


--
Darren Dunham                                           ddunham AT taos DOT com
Unix System Administrator                    Taos - The SysAdmin Company
Got some Dr Pepper?                           San Francisco, CA bay area
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