ADSM-L

Re: Tivoli storage manager migration/backup

2006-10-19 12:35:27
Subject: Re: Tivoli storage manager migration/backup
From: Robert Clark <Robert_Clark AT MAC DOT COM>
To: ADSM-L AT VM.MARIST DOT EDU
Date: Thu, 19 Oct 2006 09:17:01 -0700
On Oct 19, 2006, at 8:54 AM, Skylar Thompson wrote:

Kelly Lipp wrote:
Yes there is a way to do write to two tapes simultaneously: one
primary
and one copy.  Use the copystg parameter on the primary pool to set
this.  This action behaves with respect to the collocation
parameter on
each pool.  So if the primary pool is collocated and the copy is not,
the correct thing will happen.

Also, remember we don't mirror tapes anyway and that term is not
appropriate.  What we do is make sure that there are two copies of
the
data: one copy in the primary pool and one in the copy pool.  These
copies are created either by writing to the to pools at the time
of the
client backup (which is not always practical) or by using the backup
stgpool command.


OK. I looked at simultaneous write, but we have so many clients that
have been known to have over a terabyte of data to back up spread out
over tens of millions of files that going to tape before going to disk
seems like a bad idea.

In general, plan on writing to two tapes at the same time if the data
from the client is large.  If it is not, consider sending data to
a disk
based pool first, backing that up to the copy pool and then
migrating to
the tape pool.



Is there a way to guarantee that data is backed up to a copy tape pool
before being migrated to the primary tape pool? We want to avoid any
tape-to-tape transfers before we have two known-good copies that we
can
recover from.

Copy storage pool from disk to offsite pool. (Disk to tape.)
Copy storage pool from onsite tape pool to offsite tape pool.
(hopefully nothing)
Migrate from disk to onsite tape. (Disk to tape.)

And I guess this is as good a place as any to ask: How are other
people
mitigating the primary tape pool as a single-point of failure? What do
people consider the likelihood of tape failure between the time the
disk
cache is migrated to primary tape, and the primary tape is backed
up to
copy tape (probably ~24 hours)? For the record, we're using Ultrium3
tapes w/ hardware compression.

I haven't seen that happen. But I've not been in an LTO environment.

--
-- Skylar Thompson (skylar2 AT u.washington DOT edu)
-- Genome Sciences Department, System Administrator
-- K324, (206)-685-7354
-- University of Washington Medical Center