My thoughts on the inline vs post process debate can be found in this blog 
entry:

http://www.backupcentral.com/content/view/134/47/

What you say is mostly true.  BUT if the post processing vendor has a greater 
dedupe ratio (possibly because they can spend more TIME deduping), then it 
should help mitigate this difference.  Without going into details of each 
vendor trust me when I say they ALL have situations where they're using more 
space than the competitor.

Another reason it's not entirely true is that some post processing vendors are 
deduping during ingest just like inline vendors.  They're just doing it 
asynchronously.  If they're deduping at a rate close to the ingest rate, then 
you don't need enough disk for a whole night's backups.  You only need an hour 
or so.

Finally, the difference in space created by having an additional night's 
backups stored in its entirety (if that's how it does it) decreases 
significantly as your retention period increases.


Curtis Preston  |  VP Data Protection  
GlassHouse Technologies, Inc.
 
T: +1 760 710 2004 |  C: +1 760 419 5838 |  F: F: +1 760 710 2009  
cpreston AT glasshouse DOT com |  www.glasshouse.com
Infrastructure :: Optimized
-----Original Message-----
From: veritas-bu-bounces AT mailman.eng.auburn DOT edu 
[mailto:veritas-bu-bounces AT mailman.eng.auburn DOT edu] On Behalf Of Andrew 
Stueve
Sent: Wednesday, July 30, 2008 9:52 AM
To: veritas-BU
Subject: Re: [Veritas-bu] Exagrid

I think that "post process vs. inline" is an important issue.

We evaluated both Netapp and Data Domain, before choosing the Data 
Domain solution.   One of reasons was that processing.

Post processing, means if you are writing 4 Tb of data on a weekend 
full, you have to have 4 Tb of free disk space to write it all, and then 
it will compress down.

In-line, means that as you write that 4 Tb of data, you only have to 
have the space for the de-duped/compressed image.

I won't shill for Data Domain, since they don't pay me, but...

-Andrew

Fergus Donohue wrote:
> Hi Justin,
> 
> Thanks for the feedback. They sell a NAS based de-dupe device very 
> similar in concept to Data Domain, but it does post-process rather than 
> in-line de-dupe. Price-wise they appear very competitive and I was 
> wondering if anyone had any real-world experience with them.
> 
> Thanks,
> 
> Fergus.
> 
> Justin Piszcz wrote:
>> Never heard of or used it myself Fergus.
>>
>> Justin.
>>
>> On Wed, 30 Jul 2008, Fergus Donohue wrote:
>>
>>   
>>> Should I take the resounding silence as a "no" then? ;)
>>>
>>> Thanks,
>>>
>>> Fergus.
>>>
>>> Fergus Donohue wrote:
>>>     
>>>> Hi all,
>>>>
>>>> The question has been asked here before, but things may have moved on
>>>> since. Has anyone deployed an Exagrid solution in production and if so,
>>>> how has it been?
>>>>
>>>> Thanks,
>>>>
>>>> Fergus.
>>>> _______________________________________________
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>>>>
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>>>     
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