Hi Eric,
In a disaster, you mark your primary pool volumes "destroyed", but they
are still in your DB, along with all the appropriate file entries.
If you start backing up again, TSM just continues doing incrementals,
because the DB tells it the older files were already backed up.
To rebuild your primary pool, you can do RESTORE STGPOOL; TSM will mount
the copy pool tapes and start rebuilding the primary pool.
As each of the primary volumes gets completely rebuilt, TSM will delete
the old entry from the DB.
In the meantime, anytime somebody tries to do a RESTORE, TSM sees the
primary tape is marked DESTROYED, and automatically requests the mount
from the copy pool tape.
So I don't see the which-is-primary-which-is-copypool question to be an
issue. (You have to eventually make a 2nd copy of all the data again,
regardless).
With the advent of practical long-distance fibre and/or FCIP, several of
my customers already have implemented or are considering installing a
2nd library in the twin center and making the copy pool tapes there
directly, instead of just sending the tapes there by courier and having
them sit in a box. That's the ideal situation. You pre-install TSM on
one of the servers in the twin center (but leave it shut down); make
sure your PREPARE script also gets made to a disk in the twin center.
Then when you have your disaster, all you have to do is restore the TSM
DB, and you're ready to start restoring your clients.
An even better idea is putting the PRIMARY pool at the twin center, and
the COPY pool at your main center. That way in a disaster that hits
your clients, your TSM server is unaffected; you're ready to do restores
as soon as they give you something to restore to, and you have all your
DRIVES available.
A VTL at the remote site is also a great idea; because your restores
aren't limited then by the number of tape drives; just your bandwidth.
If you don't have a library at your twin center, you can have a couple
of manual drives there. There is no requirement for TSM to have a
library, or the same type of library. BUT, if you don't have a library,
you certainly won't be doing restores very quickly for your clients.
So it depends on what your management thinks considers their TIME
requirement to be in a disaster recovery-situation. You can be sitting
at the twin site with a box of tapes waiting for them to buy you some
hardware, or you can be ready to restore in 5 minutes - just a matter of
the $ they are willing to spend...
Wanda
-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of
Loon, E.J. van - SPLXM
Sent: Friday, September 01, 2006 7:17 AM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Making TSM twin-center compliant
Hi *SM-ers!
We are about to implement a second (fallback) IT center on another
location. The idea is to create a hot standby environment for TSM.
We are already using a separate copypool which will be moved to the new
remote location, so if the primary pool gets lost, we have all data (up
until the last backup stgpool of course) on the remote location.
However, in case of a disaster, not only will we have to be able to
recover clients (from this copypool), but we also need to continue
backup here.
This would be no problem if one could promote a TSM copypool to a
primary pool. In this case one could just continue making (the forever
incremental) backups, but TSM doesn't offer this function (yet). An
UPDATE COPYPOOL POOLTYPE=PRIMARY would be very nice to have...
The only thing I could think of is creating a standby library which can
be connected in case of a disaster to host the new primary pool and
start all over with backing up. A waste of money because it will
probably (and hopefully) never be used..
How do other twin-centers solve this?
Thank you very much for any hints and tips in advance!!!
Kindest regards,
Eric van Loon
KLM Royal Dutch Airlines
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