I don't think it's an either/or decision.  I believe that tape will always have 
a place but that using some file pool will offer very nice RTO/RPO combos for 
some data structures.  The allure of very inexpensive tape storage should 
always be there (and perhaps increase again with LTO5) while the allure of 
"instant" restore will intrigue us, especially as 2TB SATA becomes mainstream.

Power and cooling disk is expensive and not green (I'm not green either, but 
thought I should at least try to be politically correct), while tape is still 
green (except for the oil needed to make the darn things).

How about some hardware compression on the shelf based controllers?  Perhaps 
target these products specifically to the backup space.  To me, that's the 
biggest problem.

Kelly Lipp
Chief Technical Officer
www.storserver.com
719-266-8777 x7105
STORServer solves your data backup challenges. 
Once and for all.


-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of 
Richard Rhodes
Sent: Tuesday, September 22, 2009 5:41 AM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: [ADSM-L] the purpose of "file" device class

"ADSM: Dist Stor
> Hi TSM-ers!
> At this moment we are using a diskpool with a VTS-like (DL4106 by EMC)
> storage pool as nextpool.
> I too am looking at a FILE pool to replace this in the future, just to
> prevent a vendor lock-in for our TSM environment and of course the
> possibility to use de-dup.
> The only problem I see for using large FILE (100 Tb +) pools is the size
> of the filesystems on the host running the TSM server. Now it's AIX, but
> in the future we are likely to migrate to Linux.

It would be interesting to know if the VTL vendors (which are basically
implementing FILE type volumes inside the VTL) use a filesystem, raw
logical vlumes, raw disk . . . or whatever.

> Does anyone have experience with 100+ Tb FILE storagepools?
> Thanks for any reply in advance!

We keep looking at big pool of FILE devices vs VTL for our next
big purchase down the road - whether for the initial pool where
backups go directly, or are later migrated to.

We keep hitting our heads against a wall in trying to come up
with a way to make widespread use of a BIG FILE device pool:

- dedup: IBM has solved this one with v6.1!!!

- compression: To replace tape drive compression we need TSM server side
compression (or should I say FILE device pool compression).
We can't just push the job onto the clients.  VTL's
support hdwr compression via compression cards.  I wonder if IBM
will ever support server side hdwr compression via
add-on cards for FILE devices (http://www.aha.com).

- lanfree:  Provide good lanfree with FILE devices that is not
Sanergy.

We've got a couple years yet on our tape systms, but as of
today, we really don't see much way to effectively implement
a large scale FILE pool to replace our current TAPE drives.
FILE pools may be IBM strategic direction for TSM, but I think
they have a lot more work to make it a true reality.

Rick


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