VCB Snapshot crashed SQL server on GUEST

[jdoz_bw]

This is interesting. Today at 3:05 PM EST from my VCB ProxyHost I ran a vcbMounter.exe -t fullvm to copy a VM over the SAN. At the same time the SQL database on the VM guest crashed with the following events from the event log:

MSSQLSERVER 17053: LogWriter: Operating system error 1784 (The supplied user buffer is not valid for the requested operation encountered)

MSSQLSERVER 900: The log for database 'BESMgmt' is not available

MSSQLSERVER 9001: The log for database 'tempdb' is not available

What is happening here? I thought a Snapshot quiesces a VM's disk on the SAN and is not supposed to have an effect on the VM guest itself... Any thoughts or ideas are appreciated.

[doctormiru]

Hi

There are several things to consider when using VCB or manual snapshots.

It's recommended to disable the SyncDriver on guests running as domain controllers, dhcp. or exchange-servers. The Microsoft ESE (Enhanced Storage Engine) is not aware of HW-based snapshots. Restores to snapshot backups oftenly result in inconsistent databases, of course SQL or Oracle databases do not like that too.

We place databases or other data on an additional vmdk and set the virtual disk file to "independent peristent" mode. In this mode, the vmdk containing the databases is not affected by snapshot operations.

I would never build my DR plans on snapshot backups only. The applications have to be backed up using an "application aware" backup method.

Michael (dr.miru)

www.miru.ch

[dconvery]

That's why I asked if it happens if you just take a snapshot manually... Is it the snapshot that causes the crash or the Sync Driver. You can uninstall the sync driver and get a crash-consistent backup, then use the flat file to recover SQL if needed.

[doctormiru]

Hi

There are several things to consider when using VCB or manual snapshots.

It's recommended to disable the SyncDriver on guests running as domain controllers, dhcp. or exchange-servers. The Microsoft ESE (Enhanced Storage Engine) is not aware of HW-based snapshots. Restores to snapshot backups oftenly result in inconsistent databases, of course SQL or Oracle databases do not like that too.

We place databases or other data on an additional vmdk and set the virtual disk file to "independent peristent" mode. In this mode, the vmdk containing the databases is not affected by snapshot operations.

I would never build my DR plans on snapshot backups only. The applications have to be backed up using an "application aware" backup method.

Michael (dr.miru)

[dconvery]

Well said, Doc.