Application consistent snapshots with snapdrive

[#1]

I am just trying to clarify my thinking. We have snapdrive to provide us with the vss hardware initiatior and talk to the microsoft vss providers, when I use it to create a snapshot it also acts as the requestor.

Do I actually need a snapmanager for SQL if my only goal is to have a consistent snapshot of my data at a given point in time? It seems to me that when the VSS writer for SQL is registered correctly and I launch a snapshot from snapdrive it would be consistent. Obvisouly if I wanted to do a full restore with some help like a point in time restore with logs I would also use snapmanager.

The default answer is to use snapmanager, but I do not understand why a vmware snapshot (with tools installed) can be consistent (calls vss from outside and gets me an application consistent snap) while snapdrive would not be able to.

[#2]

From the VSS perspective, Snapdrive is a VSS requestor. In order to make app-consistent snapshots, a VSS requestor needs to support the specific VSS writer (the app). I don't think Snapdrive supports SQL's VSS writer, which is supported by Snapmanager for SQL. Please see the link: http://wikid.netapp.com/w/SnapDrive_for_Windows/VSS_Requester. The info might be a little old but the concepts are still correct. So, the answer is yes, you need SMSQL.

As to VMware, it could be that the VM's VSS writer is supported. By the way, I think Snapdrive talks to NetApp hardware VSS provider, not Microsoft VSS providers.

Hope that helps,

Wei

[#3]

SnapDrive does not implement a VSS requestor. So, snapshots created from SnapDrive are not application consistent.

SnapDrive has Data ONTAP VSS hardware provider which knows how to create snapshots on NetApp storage system. SnapManagers implement VSS requestor, so SnapManager snapshots are application consistent.

Thanks,

Anagha

[#4]

 I do not understand why a vmware snapshot (with tools installed) can be consistent (calls vss from outside and gets me an application consistent snap) while snapdrive would not be able to.

As Anagha already said, SnapDrive does not leverage VSS, whilst VMware snapshot does - hence implications in NetApp/VMware environment:

http://communities.netapp.com/message/8132#8132

http://communities.netapp.com/thread/6582

Regards,
Radek

[#5]

That is too bad, I know some vendors (mostly small) that provide a free and simple tool to leverage VSS consistency with the storage array.

Does this also mean that snapdrive does not leverage the NTFS writer for VSS? Basically not even the file system snap is consistent?

[#6]

I'm disappointed, because it seems that the "feature" of a VSS requestor has been on Snapdrive wish list forever (since SDW v2.0 or 2.1). Is there a plan to integrate a VSS requestor into SDW in the future?

Thanks,

Wei

[#7]

That is too bad, I know some vendors (mostly small) that provide a free and simple tool to leverage VSS consistency with the storage array.

Nothing is free - it is just included in the price of the hardware (or other software for the sake of argument). LeftHand is one of such examples, but bear in mind they cannot go (currently) beyond simplistic VSS-based consistency. And this is really no match for a fully blown (albeit chargeable SnapMager, GUI-driven backup & recovery tools with catalogs, log truncation, etc.

Does this also mean that snapdrive does not leverage the NTFS writer for VSS? Basically not even the file system snap is consistent?

SnapDrive-triggered snapshots are file system consistent - everything from file system cache gets commited to disk before taking a hardware snapshot.

Regards,

Radek