Re: Oracle backups using Snapshot Technology
- From: "Mark Brinsmead" <pythianbrinsmead@xxxxxxxxx>
- To: DIANNA.GIBBS@xxxxxxxxxxxxx
- Date: Wed, 8 Nov 2006 21:51:17 -0700
I remember a time (not so long ago) when performing backup backups with
"snapshot" technology was cutting edge, and SAN-based "server-free" backups
were considered the holy-grail of backup and recovery. Of course, that was
back in the days when the best (and most expensive) tape drive technologies
did maybe 20MB/s and cost in the neighbourhood of $50,000 each.
I had a client once who was fully prepared to spend $2Million for hardware
to backup a 600GB database -- $1Million for tape drives, and $1Million for a
massive robot (hypothetically) capable of doing 15,000 tape changes per
night.
In cases where you have really extreme backup requirements (e.g., terabyte+
database running flat-out 24x7 on the biggest hardware you can find)
snapshot technologies can be a godsend. They might be the only option
available.
But they are not cheap. On most storage platforms I have seen, "snapshot"
backups are an extr-cost option, often in the range of $50,000 to $100,000.
With modern tape drives managing sustained throughput in the neighbourhood
of 500GB/hr -- for the "enormous" cost of about $7000 per unit, you can
purchase a lot of backup throughput for the cost of the "snapshot" option
for one mid-range disk array.
Also beware of unrealistic expectations, and impossible promises. I have
actually worked at sites where the storage managers actually believed that a
"snapshot" terabyte volume could complete "nearly instantaneously". Heck, I
knew one manager who believed he could do "snapshots" of 30TB of data in
only a few minutes -- between two baby EMC disk arrays. I show him numbers
that proved that running half of the interfaces in each array flat-out,
these "snapshots" would take something on the order of 30 hours to complete,
but he knew I was wrong -- after all, the sales rep told him they were
"instant"...
In general, "snapshots" take only moments to initiate, and you can start
reading from the almost instantly. (This is the amount of time your
database needs to be in "backup" mode.) But depending on the data volumes,
they can take hours, or even days to complete. Until the snapshot has
completed -- or been read in its entirity and copied to tape -- you don't
actually have a backup. A disk failure in the "primary" storage during this
time will destroy the "snapshot", too!
Personally, I think the "snapshot" thing is really cool -- and it was even
cooler back in about 1993. But I am aware of relatively few situations
where this is actually needed.
To be honest, I think it is tough today to compete with the performance and
cost-effectiveness of locally-attached tape drives...
Can you do "snapshot"
On 11/8/06, DIANNA GIBBS <DIANNA.GIBBS@xxxxxxxxxxxxx> wrote:
We're looking at implementing a new enterprise backup solution.
Is anyone using "snapshot technology" to backup your oracle databases?
If so, could I get more info - O/S, database version, database size,
timings for putting tablespaces in backup mode (database mode if 10g),
SGA size, good things, lessons learned, comments or thoughts?
Have you tested the backup, recovered or refreshed an environment using
this technology - any issues?
What about snapshot vs RMAN - any comments?
Thanks in advance.
Dianna Gibbs
Children's Medical Center - Dallas
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//www.freelists.org/webpage/oracle-l
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Cheers,
-- Mark Brinsmead
Senior DBA,
The Pythian Group
http://www.pythian.com/blogs
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