Does ESX server do write cashing of IO on VMDK disk?

[rajeshv]

I am planning to host my application (SQL) in a VMDK disk and take backup using controller snapshot. I need to know does VMware do any IO cashing if yes how can I flush it?

Thanks,

Rajesh

[dtracey]

I don't think controller snapshots are a great way to backup SQL to be honest. You are better off looking at something that can handle the transactional aspect of the application and is aware of the need to queisce the DB if necessary.

[Gerrit_Lehr]

I totally agree with dtracey, controller snapshots will most-likely result in an inconsistend database.

Kind Regards,

Gerrit Lehr

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[rajeshv]

I am aware of the fact that controller side snapshot will

not be consistent. My question is after taking care of application consistency

can I go ahead and trigger controller snapshot or should we do something at

VMware layer?

[Gerrit_Lehr]

No you don't. ESX acknoledges the write / read operations back to the VM first when it got the ack from the controller, too. So when the database is consistend on application layer, it will be on storage level, too.

Kind Regards,

Gerrit Lehr

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[TapeshGoyal]

I heard vmware snapshot flushes the VMDK. is it true ?