I just wrapped up a pretty in depth review of both Data Domain and
Quantum/EMC and ended up purchasing the 7500's from Quantum.

Few thoughts:

- Data Domain seemed to be pushing the NAS/CIFS side a lot more than
their VTL.  OpenStorage is great and all but you limit yourself to LAN
speeds.  We definitely wanted to go VTL for the 4Gb.  Quantum has been
in the VTL game longer and I liked how they were doing it better.  In
remote sites where you might not have a SAN environment/TBs of data it
might not be as big of a deal.

- Quantum owns the Rocksoft dedupe patent and Data Domain (short version
of the story) licenses it from them.  If anyone is going to optimize the
algorithm in future versions I seriously doubt it's going to be DD.

- Yeah, the DD does inline dedupe 'better' but for the most part we have
relatively quiet times during the day when only Oracle log file grooming
is running where post processing is free to do it's thing.  I don't have
my notes in front of me with the numbers but the post-proc ingest rate
of the 7500 is higher than the inline ingest rate of the 690.  We don't
really have the need for up to the second replication of tape.
Replicating the 7500 namespace once per day is fine as we currently only
offsite physical tape once per day.  Backups are not expected to be an
up to the minute RTO, we have SRDF, etc for critical systems like that
if the walls fall down.  

- The 7500 scales better than the DD690 IMHO.  The 690 goes to, I
believe, ~25TB and the 7500 to 180TB.  DD wanted to sell us multiple 690
heads to meet the throughput of the 7500.  The downside of that is when
you have multiple heads you don't get a common block pool.  So you
backup the same block of data to one head and it is also stored on the
second head and your global dedupe ratio is reduced.  There is supposed
to be a solution for this in the future (I don't believe this is NDA)
but how it will work and what it does for performance, etc I don't know.

- RAID 6 - DD does it, Quantum/EMC currently doesn't.  Is it that big of
a deal?  We haven't had a drive failure yet.  I'm sure rebuild times
will be dependent upon how hard you are hitting it.  If you have a less
busy time it might not matter at all, if you are driving it full speed
24x7 it might.

Robin - Feel free to drop me an email directly if you want to ask me
anything.

Geoff Stafford
Barclaycard US
Data Protection Engineering
office: 
mobile: 


Barclays             www.barclaycardus.com

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