HPE StoreVirtual Storage / LeftHand
cancel
Showing results for 
Search instead for 
Did you mean: 

Snapshot of Exchange 2010 purges logfiles

Paul Hutchings
Super Advisor

Snapshot of Exchange 2010 purges logfiles

Hi,

I have my Exchange 2010 databases on volumes on a P4000 running 9.0.

The Exchange server has the HP VSS tools installed.

When I create a managed snapshot from the CMC it correctly detects that there are 2 volumes, however it also purges the Exchange transaction logs which I did NOT expect to happen - I only expected that the application aware snapshot would make a consistent snapshot.

Is this normal behaviour please?
7 REPLIES
Patrick Terlisten
Honored Contributor

Re: Snapshot of Exchange 2010 purges logfiles

Hello Paul,

AFAIK this is a "feature" of the VSS support of Exchange 2010. So this is by design.

Regards,
Patrick
Best regards,
Patrick
Paul Hutchings
Super Advisor

Re: Snapshot of Exchange 2010 purges logfiles

Thanks Patrick, I guess it can't be changed to NOT purge the logs then?
Jitun
HPE Pro

Re: Snapshot of Exchange 2010 purges logfiles

You can configure Exchange to save disk space by enabling circular logging. Circular logging allows Exchange to overwrite transaction log files after the data that the log files contain is committed to the database. However, if circular logging is enabled, you can recover data only up until the last full backup. For example, you can enable circular logging when using Exchange Native Data Protection, in which you don't make backups. Therefore, to prevent log buildup, you need to enable circular logging.

In the standard transaction logging that is used by Exchange 2010, each database transaction is written to a log file and then to the database. When a log file reaches one megabyte (MB) in size, it is renamed and a new log file is created. Over time, this results in a set of log files. If Exchange stops unexpectedly, you can recover the transactions by replaying the data from these log files into the database. Circular logging overwrites and reuses the first log file after the data it contains has been written to the database.

In Exchange 2010, circular logging is disabled by default. By enabling it, you reduce drive storage space requirements. However, without a complete set of transaction log files, you cannot recover any data more recent than the last full backup. Therefore, in a normal production environment, circular logging is not recommended.

Hope this helps.
--------------------------------------------------------------
How to assign points? Click the KUDOS! star!
Paul Hutchings
Super Advisor

Re: Snapshot of Exchange 2010 purges logfiles

Jitun,

Thanks for the info, but it's not really the same thing that I'm asking.

I know how the Exchange logs work and how circular logging works and the advantages/disadvantages.

What I didn't expect was that creating an application aware snapshot in the P4000 would purge the transaction logs.

This is the first SAN we've had with a VSS component so it may be that this is normal on all such SANs.

Paul
Jitun
HPE Pro

Re: Snapshot of Exchange 2010 purges logfiles

Transaction logs can grow at a fast pace as each and every transaction is recorded to the log files.
There are two ways to manage this growth with the recommended method being a regular full backup of the Information Store.

Upon successful backup, the transactions are committed to the database and then purged.
--------------------------------------------------------------
How to assign points? Click the KUDOS! star!
Paul Hutchings
Super Advisor

Re: Snapshot of Exchange 2010 purges logfiles

What we do right now is a full daily backup, and several incremental backups daily which purges the transaction logs.

Where I'm struggling seeing the benefit of using Application Managed snapshots is because if that purges the transaction logs, it means I can't do a consistent incremental backup using our backup software because there will be 2 different products (the software & the P4000) telling Exchange to purge the transaction logs.

So I guess I'm wondering what other folks who have Exchange 2010 and a P4000 do?
Ben Drawbaugh
Occasional Advisor

Re: Snapshot of Exchange 2010 purges logfiles

What I do is to not do application aware snapshots on my exchange DB volumes. I do regular snapshots which I know are probably useless, but figure its better to have a second backup that might work, than just a single backup.

I do agree that an application aware backup that does not clear the logs could be useful, but question weather this is something HP could implement or if it is a VSS specific setting, and thus on Microsoft to address.