Re: [ADSM-L] FW: [ADSM-L] Data Deduplication

2007-08-30 03:41:50
Subject: Re: [ADSM-L] FW: [ADSM-L] Data Deduplication
From: Curtis Preston <cpreston AT GLASSHOUSE DOT COM>
Date: Thu, 30 Aug 2007 03:39:36 -0400
>I am 100% with you on the "why replicate backup" when you can more
>easily replicate data?!  

If you've done away with traditional backup, then I'd agree.  If you're
still making tapes (or virtual tapes), then you also want those tapes
offsite.  You've got two choices: hand them to a dude in a truck or
replicate them.  Replicating them may cost a bit more (but it's still a
lot more feasible now due to de-dupe), but you won't lose a tape and
have to go on CNN.

>I think money is better spent there than on
>replicating backup data.  But try convincing a customer that's had the
>Kool-Aid that they don't want de-duplication!

Since I'm passing out the Kool-Aid, I'll answer. ;)

De-dupe really does make sense, even for TSM shops.  Storing (and
leaving) backups on disk is definitely the future, and de-dupe makes it
5-10 times cheaper.  It just makes sense.

Replication and snapshots (which I call near-CDP) is far superior to
backup in many ways, and the Compellent story is very nice, as they
allow you to have many snapshots without a performance penalty.

But I see replication as the thing to do once you've straightened out
your backup.  It's still not a complete replacement. It accomplishes
things backup doesn't, but backup accomplishes things that near-CDP


If you're going to have backup, you're going to want it off-site.  Go
back to the beginning of the post.

>Your comment about management classes is right on!  If you limit the
>number of version of a db backup that you keep to something reasonable,
>like seven, let's say and with a 1TB database (which is big!), then you
>have 7TB worst case of duplicate data!  Let's see: that breaks down to
>about 7 LTO4 tapes.  Or 10 750GB SATA drives.  Or 7 x $100 = $700 for
>tape, plus slots of course so let's say $2000.  For disk, depending on
>your vendor, that could cost between $3K and $8K (and if you're paying
>more than that for SATA drives you perhaps ought to seek counseling!).
>So how much would  you be willing to spend to reduce this cost?  No
>than $8K.  Does a DD cost less than that?  I'm not thinking so.  And
>unless my math is way off you can make a reasonable argument against
>even more db data!'

Your math is definitely off.  No offense, but you are making the classic
mistake of looking only at the cost of the media.  Those tapes are
worthless without a really expensive tape library around them.  Having
said that, we really need to start talking about 30-50 TB of backed up
data before the de-dupe boxes come into play.

>It's all about mind share, isn't it?  Today, de-duplication is hot...

I've been in this business about 14 years, and I've never seen a
technology get adopted this quickly.  It's going to happen.  It is
happening.  It's not a fad.  It just makes sense.

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