Crash-consistent backups in VDP

[omaggi81]

Hi everybody

I have installed the vSphere Data Protection 6.1 and since few days the backup of a VM is "crash-consistent". The other VMs don't have this problem and all the backups are "application-consistent".

What is the meaning of this type of backup?

What can I do to solve this issue?

Thx in advance, sincerely Omar

[rutgerblommah]

Application-consistent is generally what you want. It requires that VMware Tools is installed and running on the guest. Without VMware Tools installed and running you end up with crash-consistent backups which simply put means the guest OS will survive a restore, but you might end up with application data problems. Especially if you're running a database on a guest you want to make sure you are producing application-consistent backups.

[SavkoorSuhas]

Okay so this is the deal with backups:

You have two types here:

Application consistent and Crash Consistent

With crash consistent backup is backing up the VM state which it was in when the backup request was initiated.

Any data in memory or in-transaction data is not backed up.

With application consistent backup, the data in the VM state during backup request along with data in memory and in-transaction data is backed up

This is what is chosen for database based applications.

Now, Windows provides VSS for application based quiescing. You have VSS Requestor, Provider and Writer which work together to take a quiesce snapshot of the VM.

Application consistent backup is received when only a quiesce snapshot is performed.

Now Linux VM backups are always crash consistent backups as they do not have any VSS daemons. Unless your have a pre-freeze / post-thaw script, the VM will backed up as crash consistent.

Now, In VDP, you have an option to fail back to non quiesce if the quiesce task fails. By default, VDP does a quiesce snapshot (Unless disabled by adding a parameter in avvcbimageCMD.all file to disable quiescing completely)

So if you are receiving only crash consistent backups for a VM which initially used to provide application consistent backups, then I would suggest you to look at the logs of the backup located in "/usr/local/avamarclient/var/Job-Name-EPOCH-imagew.log

You can search for the term "quiesce" if quiesceFS=0 it is a non-quiesce snapshot and the backup is crash consistent

if quiesceFS (QuiesceFileSystem) = 1 then it is a quiesce snapshot and the backup will be application consistent.

Hope this helps.

Suhas

[omaggi81]

Thank you so much for the perfect explaination

Have a good days, greetings Omar