I have now verified with two other de-dupe vendors (Falconstor &
SEPATON) that Oracle multiplexing is not an issue for them.  (I also
have a question in to Diligent to verify that this accurately reflects
the way their product works.  They said they would get back to me
today.)

Having said that, I think this does present something to test with any
de-dupe product you are considering.  I knew that multiplexing in NW and
NBU might be an issue for some de-dupe products, but I never thought
about multiplexing in Oracle might be an issue.  I wonder what other
apps might munge data together like this in their backup streams...

---
W. Curtis Preston
Backup Blog @ www.backupcentral.com
VP Data Protection, GlassHouse Technologies 

-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of
Charles A Hart
Sent: Monday, August 27, 2007 10:53 AM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: [ADSM-L] Data Deduplication

According to Dilligent, when RMAN uses Multiplexing, it  intermingles
the
data from each RMAN so the data block will be different every time so
the
blocks are different, similar to Multiplexing with Netbackup...   I'm
not
an RMAN expert, just trusting what the Vendor is stating.

The following link seems to match with what we are being told

http://download.oracle.com/docs/cd/B19306_01/backup.102/b14191/rcmconc10
02.htm
 (Look for the Multiplex Section)

Is there an RMAn expert in the house?  Can some one confirm this info?

Charles Hart
UHT - Data Protection
(763)744-2263
Sharepoint:
http://unitedteams.uhc.com/uht/EnterpriseStorage/DataProtection/default.
aspx




Curtis Preston <cpreston AT GLASSHOUSE DOT COM>
Sent by: "ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>
08/27/2007 11:40 AM
Please respond to
"ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>


To
ADSM-L AT VM.MARIST DOT EDU
cc

Subject
Re: [ADSM-L] Data Deduplication






>        3) Oracle Specific
>                Do not use RMAN's Multiplexing in RMAN will combine 4
>Channels together and the backup data then will be unique every time
thus
>not allowing for                        de-duping)
>                Use the File Seq=1 (Then run multiple channels)

I don't see how this would affect de-duplication if your de-dupe product
knows what it's doing.  Every block coming into the device should be
compared to every other block ever seen by the device.  So combining
multiple files together using Oracle multiplexing shouldn't affect
de-dupe.

Did you test this, or see it in the docs somewhere?  Was this true for
multiple de-dupe vendors, or just the one you chose?



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