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Re: Anyone use SAN based demand-allocated snapshots of Exchange 2007 SP1 Database LUNs?

 
Adam Garsha
Valued Contributor

Anyone use SAN based demand-allocated snapshots of Exchange 2007 SP1 Database LUNs?

Do you have problems with large growth of the copy-on-write snapshots? Have you worked around this problem by adjusting settings on the exchange server side? If so, share your magic and enjoy my gratitude and points!
6 REPLIES 6
Gfuss
Trusted Contributor

Re: Anyone use SAN based demand-allocated snapshots of Exchange 2007 SP1 Database LUNs?

Adam,
I'm not doing copy-on-write snapshots, however, I can see where the data is going to grow exponentially until you have no data storage left. I realize the snapshots will not be larger than the source as they are delta files, however, you are going to constantly be creating them.

If I understand this correctly, each time a change is made to the Exchange LUN, you are creating a snapshot. I would assume every transaction (e.g. e-mail, setting change) is going to fire off a snapshot.

What are you trying to accomplish (e.g. disaster recovery, high availability)? Is the Exchange server with the MB role doing any LCR or CCR?

More questions than answers!!

-Gfuss
Adam Garsha
Valued Contributor

Re: Anyone use SAN based demand-allocated snapshots of Exchange 2007 SP1 Database LUNs?

No I am talking about single snapshot, one per day. I am saying the Delta is growing more quickly than one would expect. Any other database much less growth of delta. Something is churning data in exchange. Namely, something is re-writing blocks back to disk. It only takes a few hours and every data block has been re-written (hence large delta).
Gfuss
Trusted Contributor

Re: Anyone use SAN based demand-allocated snapshots of Exchange 2007 SP1 Database LUNs?

I'd compare the time that the maintenance runs on your Exchange DB with the time the snapshot is getting taken.

Each time a new mailbox database is created, a maintenance time is automatically selected.

This is found on the Properties of the Mailbox Database and I believe it is usually 1-3am by default.

I'm wondering if you adjust the snapshot to be after the maintenance, if that will decrease the size of the delta.

Let me know what you find.

-Gfuss
Adam Garsha
Valued Contributor

Re: Anyone use SAN based demand-allocated snapshots of Exchange 2007 SP1 Database LUNs?

Good insight, we too thought maybe defrag so we disabled database maintenance and we still see the problem. I also tried taking the snapshot at different times (even during the day) and they all behave the same. They grow to roughly size of data in just a matter of 2-3 hours. One would expect much less; most databases, I see <10% growth of snap in 24-hours.
Adam Garsha
Valued Contributor

Re: Anyone use SAN based demand-allocated snapshots of Exchange 2007 SP1 Database LUNs?

I should add that I was incorrect about being at SP1... we are on pre-release SP2 (to fix some UM integration issues we had been having).

I didn't try the snapshots while we were only at SP1 so I don't know if same behavior.
Gfuss
Trusted Contributor

Re: Anyone use SAN based demand-allocated snapshots of Exchange 2007 SP1 Database LUNs?

Adam,
This may/not help, but here's a page detailing what causes the DB to change/grow rapidly: http://tinyurl.com/bdgv3a

That wouldn't explain why the delta file itself is growing to the same size as the original, however, it may offer some insight.

-Gfuss