Ensuring Consistent Image-Based Backup for App Databases Like SQL Server with vRanger Pro 4.5

One of the new features shipping in the vRanger Pro 4.5 version, is the Vizioncore VSS driver. Having the driver ensures that applications with databases which are VSS-aware, are backed up at a current consistency point.

I've written about the details of how the VSS driver is implemented to work, in an earlier posting in this blog series.

How Can You Tell if the VZ VSS Driver will Ensure Consistency for Your App?

Microsoft defined its Virtual Shadow Copy Service (VSS) with an API to support software implemented to be either VSS writers or VSS requesters. For more on the VSS API, you can read about it on the Microsoft online reference library.

The important thing to know for backup, is that to get a consistent image of the database from VMware the following things must be true:

  • The application must be written as a VSS writer
  • The backup application must be written as a VSS requestor
  • The VSS implementation present in the platform must be implemented to operate correctly

As it turns out, and has been blogged about previously, VMware has not implemented VSS to operate correctly for Windows 2003 and 2008 guests. Which is why the Vizioncore VSS driver is required.

vRanger Pro is a VSS requestor, and will invoke the Vizioncore VSS driver when it is present in the guest as part of the backup process. Good so far.

Now, how do you know if the application is implemented as a VSS writer? Most applications with databases that run on Windows are implemented as VSS writers. VSS has been in the market for a long while now, and is the standard for ensuring database consistency on the platform. This includes the applications from Microsoft including Exchange, SQL Server, and others. This also includes Oracle and other database implementations.

But, different versions of each of the applications exist and you want to be able to know definitively whether a particular version deployed in your environment is implemented as a VSS writer. To make this possible, Microsoft offers a command in Windows which is: vssadmin list writers

This command lists the Volume Shadow Copy Service writers and the current state of each writer. You can use this command to confirm that the applications present in the guest are implemented as VSS writers, and therefore that they will be backed up in a consistent state by vRanger Pro working with the Vizioncore VSS driver.

Do you need TCP/P communications with every guest using the Vizioncore VSS driver?

No. The driver is implemented to avoid the need for open IP addresses allocated to every guest. TCP/IP communications to each guest is not necessary. The trade-off is that you must deploy the VSS driver into the guest. The VSS driver is small .exe file. It must be copied into the guest, and it is a one-time setup process. You do need to select the correct version of the VSS driver, for either 32-bit or 64-bit.

Anonymous