Re: [Networker] tape capacity

2005-04-25 16:06:32
Subject: Re: [Networker] tape capacity
From: Davina Treiber <Treiber AT HOTPOP DOT COM>
Date: Mon, 25 Apr 2005 20:59:43 +0100
Jon Fraley wrote:
> My jukebox has LTO-2 tape drives in it.  I am trying to figure out why
> some tapes are marked full at 205-207GB and others get up to 400GB
> running the same groups to them.  These are all brand new tapes and
> drives.  

The other responses are all valid, but there is another possibility. You
may not actually be using compression on all of the drives. Do you have
a mixture of storage nodes, perhaps even different operating systems?
There are various factors that might influence this, for example:

Solaris: different device names, cbn, hbn etc, or different settings in
HP-UX: Different tape drivers or different settings on the devices.
AIX: settings in SMIT.

205-207GB is the native capacity of the drives, so if you ARE using
compression, then the data being written is extremely incompressible,
unlikely for mixed filesystem data unless your applications are creating
vast amounts of zip files.

Another possibility is that you are using software compression on some
clients, thus causing NetWorker to report the capacity differently.
Opinions differ, but I believe that in most cases you are best to let
the drives take care of the compression rather than the clients.

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