Hi Rick!
Quite a coincident: I just spoke to DataDomain too!
1) The Dutch guys also confirmed that compressed data is dedupable, but it
depends how compression is done. If it's file level compression, you can expect
that a copy of that file is similar and thus dedupable. A compressed
ntkernel.dll from system A is similar to a compressed ntkernel.dll from system
B.
2) and 3) The Dutch DD guys stated that most TSM users with a DataDomain
appliance use a storagepool type=disk!
Normally you don't want to store your data in a diskpool, because it becomes
heavily fragmented overtime, but since the DD appliance does backend
defragmentation, front-end fragmentation on you diskpool this will have no
negative effect on performance.
I found it a very interesting option, since the appliance does in-band and
on-the-fly deduplication, compression and defragmentation and has the option to
duplicate the de-duplicated data to a remote location.
Kind regards,
Eric van Loon
KLM Royal Dutch Airlines
-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of
Richard Rhodes
Sent: maandag 15 juni 2009 15:29
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Data Domain - questions from a meeting with DD
Hello,
The other day we had a meeting with Data Domain - just the
normal vendor update about their products. While informative,
several comments were made by DD systems that I thought I
like your opinions on. (note: we are a all tape shop, and
probably will be until the next hardware refresh in several years)
Interesting comments DD made:
1) de-dup of compressed data.
We told them that much of our backup load comes from Oracle
backups that are already compressed via Unix compress utility
then pushed to TSM. We asked what effect this would have on
de-dup. They said we could expect a 4x-5x de-dup ratio on
this compress data. I had always thought that compressed data
would not de-dup.
2) NFS mounted storage pools.
They said that the vast majority of their installations,
including TSM installations, use NFS (some OpenStorage for
NetBackup, and a little CIFS) for backups to disk. In other
words, VTL emulation is a very small percentage of their
installations. If you have DD hdwr, are you using NFS
or file devices, or, a vtl interface? Is anyone using NFS
for a storage pool?
3) DD reclaim of scratch tapes
I asked about when/how DD will reclaim no longer used space.
In other words, when a scratch tape passed reuse-delay. He
said that DD had some kind of interface to backup softw such
that it knows when data is no longer needed and reclaimes that
space. I know TSM v5.5 has a feature to clear a vol when no
longer used with a vtl, but DD was saying they had a special
interface to accomplish this. Does DD have a special interface
to TSM?
Thanks
Rick
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