Right – it saves you SOME tape
(assuming it is not all unique as mentioned below) because you do initial
backups to disk and only send your duplicates to tape. While you can get
major compression/deduplication on the disk images the duplicates on tape will
be the same size they always were because it is undeduped (reduped?) when it
goes to tape. It did save us money on tape because now we only have the
offsite stuff on tape.
You can eliminate tape entirely if you use
something like Data Domain (deduplication) as it allows you to have an offsite
unit that syncs data from the onsite unit. Of course you’d have to work
out what you were going to do for DR in such a model. (e.g. Ship the offsite
unit to DR site after declaring or keep the offsite unit at the DR site –
driven by whether you own the DR site or not I imagine.)
From:
veritas-bu-bounces AT mailman.eng.auburn DOT edu
[mailto:veritas-bu-bounces AT mailman.eng.auburn DOT edu] On Behalf Of Ed Wilts
Sent: Monday, May 04, 2009 1:11 PM
To: Harmon, Patricia K.
Cc:
veritas-bu AT mailman.eng.auburn DOT edu
Subject: Re: [Veritas-bu]
NetBackup long retention does dedup help
On Mon, May 4, 2009 at 11:41 AM, Harmon, Patricia K. <PHarmon AT tecoenergy DOT com> wrote:
We backup about 45t a week that has a
retention of 8 years. We backup to disk and dup to LTO3 tapes with
few issues. Except the tape budget is killing us.
Anybody out there have long retentions? Does
de-dupe help save tapes? We have few restores, so keeping data on disk is
not a priority with us.
As always, it depends. If you're backing up the same 45TB every
week, then de-dupe will be very beneficial to you. If you're backing up 45TB of
unique data every week, and the data blocks don't match what you backed up any
other week, then you won't de-dupe at all. For example, if those 45TB
happen to be tiff images of customer statements, then forget about it. If
they're C: drive backups of 10,000 Windows servers, then you'll probably de-dupe
very, very well.
You need to do a thorough analysis of what the data is you're backing
up. The first objective, of course, is to back up less. If you can
identify 800GB, and that's only 1.7%, of your data that doesn't need to be
backed up, and assuming that you're getting 2:1 compression so you use 1 less
tape per week, then you've saved about 52*8 tapes at roughly $25 per tape, or
$10K over 8 years.
Don't forget that de-duping isn't an all-or-nothing solution. You may
de-dupe in some places where it makes sense but not others.
.../Ed
Ed Wilts, RHCE, BCFP, BCSD, SCSP, SCSE
ewilts AT ewilts DOT org
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