Exchange Server crash after a backup with VCB

Exchange Server crash after a backup with VCB

Sunday, 28 December 2008 14:22

How often did it happen while you'r back-up a virtual machine like a domain controller or Exchange server under load it's crashes? Microsoft Exchange Server or other server on a Virtual Machine Can Freeze Under Load When You Take Quiesced Snapshots or Use Custom Quiescing Scripts.

This problem is caused by a conflict between the SYNC driver, an optional feature that you install when installing VMware Tools. If installed, the SYNC driver holds incoming I/O writes while it flushes all dirty data to a disk, thus making file systems consistent. Under heavy loads, the delay in I/O can become too long, which affects many time-sensitive applications, including Exchange Server or domain controllers. If writes issued by Domain or Exchange Server get delayed for too long, the Server stops and issues error messages.

To avoid this problem, you can disable the SYNC driver before taking a snapshot. But I know, this is not a permanent solution. So is there a solution? NO

VCB is still not mature enough. But this works as workarround!

Disabling the VCB SYNC Driver (LGTO_Sync)

Disabling the SYNC driver allows you to keep the Exchange Server on-line, but results in snapshots being only crash-consistent.

To disable the VCB SYNC driver:

In Device Manager, click View > Show hidden devices.
Expand Non-Plug and Play Drivers.
Right-click Sync Driver and click Disable.
Click Yes twice to disable the device and restart the computer.

Stopping Exchange Server

Use the following pre-freeze and post-thaw scripts to take Exchange Server offline for approximately 60 seconds and then restart it again after the snapshot is taken. This approach leaves Exchange Server inactive, but keeps the SYNC driver enabled while the snapshot is taken, ensuring application consistency. Using this method, you create the quiesced snapshot of Exchange Server.

C:\Windows\pre-freeze-script.bat

@echo off
net stop MSExchangeSA /yes
net stop MSExchangeSA /yes

C:\Windows\post-thaw-script.bat

@echo off
Net Start MsExchangeSA
Net Start MsExchangeIS
Net Start MsExchangeMTA