During Oxford 2005, IBM stated that the File Device Class is the strategic data 
structure.  One can see this in action with the dedup functionality in V6.

Our products use DISK for cachepool usually deployed on JBOD arranged FAST disk 
(SAS or FC at 15K) as the initial target for client backups, particularly for 
large numbers of clients with small data movement.

File Device class is used for large amounts of storage (since we can have 
reclamation there).  Our pools are targeted by clients moving a lot of data 
daily, or are the target of migration from the cachepool.

I think both are still valid for the reasons already described but in the long 
run DISK may go the way of the dinosaur.

Kelly Lipp
CTO
STORServer, Inc.
485-B Elkton Drive
Colorado Springs, CO 80907
719-266-8777 x7105
www.storserver.com


-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of 
David McClelland
Sent: Monday, September 21, 2009 9:52 AM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: [ADSM-L] the purpose of "file" device class

Just to be uber-picky, FILE volumes now do allow multiple sessions/processes
to read/write concurrently to a single FILE volume from TSM 5.5 onwards
(http://publib.boulder.ibm.com/infocenter/tivihelp/v1r1/topic/com.ibm.itsmms
munn.doc/anrsgd5515.htm#wq28).

The big picture as I've read it is that IBM are perhaps angling the
user-base towards using FILE volumes, and that new developments would be
implemented against FILE technology rather than DISK. That being said, it's
fair to say that many people are simply more comfortable with the ease,
simplicity and habit of implementing and managing DISK volumes.

/DMc

-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of
Shawn Drew
Sent: 21 September 2009 15:58
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: [ADSM-L] the purpose of "file" device class

Disk Based (Random access) lets you have several sessions all sending data
to it.  This removes the need to queue backups like all the competitors.
But it will fragment as data expires and there is no defrag for random
access.

File devices (Sequential access) do also fragment over time, just like
tape, but you are able to run reclamation on them.  But sequential access
would cause queuing.
They each have different pro's and con's which make them suited for
different tasks.  (long term vs short term storage)

Regards,
Shawn
________________________________________________
Shawn Drew


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