There is CPU impact from calculating the MD5 sums on each block as well as storage overhead for keeping track of all the blocks in the system, to compare them for deduplicating.

The magnitude of the impact will probably be proportional to both the number of unique files/blocks in the system and the frequency of updates.

There is no such thing as a free lunch, sorry.

From: owner-toasters@mathworks.com [mailto:owner-toasters@mathworks.com] On Behalf Of Kevin Parker
Sent: Saturday, 27 October 2007 5:24 AM
To: Page, Jeremy; toasters@mathworks.com
Subject: RE: A-SIS questions

J: pretty sure it has no/minimal impact since it is performing the equivalent of a snapshot operation of just dropping a pointer to blocks of data. It also has to mark blocks of disk as 'clean' now that they're free. Minimal impact. Also consider that asis requires nearstore option which will additional 256k of ram for additional snapmirror stream that it allows. Again, vry minimal impact.
 
As to snapmirror footprint...it will send 700m over, but if dest. Isn't SIS'd, it will return to 1gb
 
I could be wrong in both points above so open to be corrected.
 
Good weekend to all.
**Sent using wireless handheld...
please excuse any typo's or brevity**
Kevin Parker - NWN Corporation
www.nwnit.com
 
-----Original Message-----
From: "Page, Jeremy" <jeremy.page@gilbarco.com>
To: "toasters@mathworks.com" <toasters@mathworks.com>
Sent: 10/26/2007 3:10 PM
Subject: A-SIS questions
 

I have read some of the info on how A-SIS works but I have a couple of questions:

1) Assuming an average compression  rate (say /home with random docs in it) how much of a performance hit does it impose

2) Does it change how much data is sent over the wire when you use SnapMirror/SnapVault? I.e. if I get 30% compression on a 1 gig snapshot do I send 1 gig or 700 mb to update my target?

Oh, and for the folks who helped earlier, we are moving our Oracle and ESX systems to NetApp, the pSeries will be fibre connected, at least at first but the ESX stuff is all going on NFS.

~Jeremy

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