Eric,
The fragmentation occurs because of aggregates.  The files within the
aggregates expire but the space isn't freed up until all the files in an
aggregate expire.
Jim Sporer


  At 11:14 AM 6/2/2004 +0200, you wrote:

Hi Jim!
> I know that this will involve running reclamation on the ATA storage pool
but we felt using a DISK device class would waste to much storage because of
fragmentation.

Why did you think fragmentation was a waste of space? If a file expires, the
space it allocated on a diskpool becomes free space, so it shouldn't be
considered wasted.
I can imagine that when a lot of little files expire, one gets a lot of
fragmented free space, which could have impact on the specific disks
performance in the long run.
Funny to see that a lot of people (including us) are thinking about SATA
storage for their backups. There doesn't seem to be anybody with real
hands-on experience however...
Kindest regards,
Eric van Loon
KLM Royal Dutch Airlines


-----Original Message-----
From: Jim Sporer [mailto:james.sporer AT DOIT.WISC DOT EDU]
Sent: Tuesday, June 01, 2004 21:37
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: D2D backup with TSM


We are going to try disk only backups using ATA storage.  We've decided to
use use a FILE device class for the ATA storage pool and do the backups
directly to the ATA storage pool.  We will back up the data to a copy
storage pool defined on a 3494 tape library.  I know that this will involve
running reclamation on the ATA storage pool but we felt using a DISK device
class would waste to much storage because of fragmentation.
Jim Sporer
University of Wisconsin

  At 10:05 PM 5/28/2004 -0400, you wrote:
>We recently had a presentation from EMC.  During this presentation
>they discussed their new DL700
>virtual tape library.  It got people talking about a long
>term strategy of moving to a all disk based backup system.  So we
>started thinking of the pros and cons of how to go about setting up TSM
>for a disk based backup system.
>
>Here are some initial thought on ways to configure TSM for D2D
>backups.  We would be very interested in your thoughts/comments.  I
>doubt we are the only people thinking about this topic.
>
>1)Purchase a very large disk system (ata drives?) and put storage pools on
>them.
>     - use a standard DISK device pool for backups
>         - how to reclaim space?  do you even need to?
>         - fragmentation problems?
>         - multiple node access concurrently
>     - use a FILE device based pool
>         - single node access per disk file volume
>         - need to run reclamation
>         - still stage to disk and migrate to FILE device based pool?
>     - use a tape copy pool for offsite and backup
>     - use a offsite disk pool somehow
>         - iscsi over lan or fc if close enough (enough throughput?)
>         - other?
>     - must use client compression to get data compressed
>         - we mostly don't do this today
>
>2)  Purchase a virtual tape system like the DL700
>     (bundle of a EMC Clariion and a FalconStor vts appliance)
>     - provides compression for data
>     - appliance is responsible for layout and use of disk space
>     - can copy a virtual tape to a real physical tape for offsite storage
>
>
>Thanks
>
>Rick


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