I have about 6TB of san disk space used for nightly backups and the
management of it is just a pain.  For instance if you are using a vendor
such as HP for your san disks the compatibility with IBM equipment is
not the greatest.  We use HP EMA 12000 with hsg80 san storage
controllers.  TSM will max out the I/O to the san controllers then the
particular lun will hang and then the san storage controller must be
rebooted to get the lun accessible again to aix but even after the
reboot the lun is available to aix but unreadable so now I lost all the
data on that lun.  I have run into this problem many times over the past
few years.  HP says disable caching at the controller level which may
work but disk I/O will be extremely slow so that is not an option.  

You can attribute these problems to incompatible hardware but I would
run what ever disk storage you choose through the ringer before you
commit to it because I have had this problem with other san storage
units as well.  We also keep disk storage in multiple locations across
campus via long haul san connections which mean multiple luns to manage
and many filesystems which if you are in an HACMP configuration takes
time for failover to occur and filesystem mounts to take place.

In conclusion make sure what ever storage you choose is reliable and
able to handle the high I/O load tsm will can on it.

-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of
Paul Zarnowski
Sent: Thursday, November 24, 2005 8:40 AM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: VTS or san disk storage

At 11:33 AM 11/23/2005, Dearman, Richard wrote:
>We currently use several TB of san based disk storage for our daily
>backups which gets migrated during the day to multiple tape libraries.
>The san disk administration has become a nightmare [...]

I am curious what kind of problems you are running into.  At the TSM
Symposium at Oxford this year, IBM indicated that they were going to
further develop the serial access disk support in TSM.  And, TSM 5.3
just added the ability for a SAD devclass to span multiple
filesystems.  After hearing this, we have been leaning towards
investing in inexpensive disk managed by TSM rather than buying a VTL
appliance.  I'm interested in other's comments about where,
specifically, they are having problems managing SAD directly by TSM.

..Paul



--
Paul Zarnowski                            Ph: 607-255-4757
Manager, Storage Systems                  Fx: 607-255-8521
719 Rhodes Hall, Ithaca, NY 14853-3801    Em: psz1 AT cornell DOT edu

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