ADSM-L

Re: [ADSM-L] TSM with DiskXtender

2009-04-27 14:03:38
Subject: Re: [ADSM-L] TSM with DiskXtender
From: "Schneider, John" <John.Schneider AT MERCY DOT NET>
To: ADSM-L AT VM.MARIST DOT EDU
Date: Mon, 27 Apr 2009 13:01:56 -0500
Neil,
        I don't support this today, but I have in the past.  Your
satisfaction with this solution will entirely depend on the requirements
of the application you are protecting, and everyone's expectations.
        If you intend for the DiskXtender data to reside on TSM tape,
you had just better be aware of the fact that when the users or
application need a file back, they may be looking at 3-15 minutes
typically to get to the first byte of data.  If this happens very
rarely, and your users anticipate this, then no one will mind. But if
you expect to be doing dozens of these a day, nobody will like it. 
        This configuration could also cause you problems if it is an
application needing to retrieve the data.  How will the application
behave if it has to wait 15 minutes for a file back?  Will the users of
the application get notified of the reason for the delay, or will their
application just clock for 15 minutes?  Or worse yet, will the entire
application shared by hundreds of users completely hang because one user
is waiting for a retrieve?  You will want to test for things like that.
        This configuration can also snowball.  I had a customer once who
set this up for PACS data (medical images).  One patient study would
have dozens of files associated with it.  So when the application
accessed a patient study for a radiologist to look at, it would try to
copy the first file...  Oh wait, TSM has to retrieve it; wait 5 minutes.
OK, got it.  Now copy the next file.  Oh wait, TSM has to retrieve it;
wait 2 minutes.  And so on.  Most of the images would have been created
together and therefore be on the same tape, but they would not be in the
same place on the tape, and not in the order in which the application
asked for them, and each retrieve was a separate TSM session that
required a reposition of the tape to find the file.  It typically took 2
hours to get a study back, and in the meantime a radiologist would be
forced to wait.  Fortunately we never went production with this
solution.
        

Best Regards,

John D. Schneider 
Phone: 314-364-3150 
Cell: 314-750-8721
Email:  John.Schneider AT Mercy DOT net 


-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of
Strand, Neil B.
Sent: Monday, April 27, 2009 11:21 AM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: [ADSM-L] TSM with DiskXtender

Is anyone using TSM as a media device for DiskXtender?
- If so, would you be willing to share your experience?

I am looking at using TSM as a cost effective alternative to adding disk
storage to our growing DiskXtender environment.

Thank you

Neil Strand
Storage Engineer - Legg Mason
Baltimore, MD.
(410) 580-7491
Whatever you can do or believe you can, begin it.
Boldness has genius, power and magic.


-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of
Joerg Pohlmann
Sent: Monday, April 27, 2009 10:47 AM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: [ADSM-L] Select with TSM 6.1

Thanks Richard, that did the trick. Very good detective work and much
appreciated.
________________________
Joerg Pohlmann
250-245-9863

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