jedijeff
Enthusiast
Enthusiast

Ensuring consistent replication with ESX and Netapp

I hope I can explain my situation correctly.

We are using a Netapp with our ESX(nfs datastore) and have a 2nd netapp doing replication via snapshots I believe(someone else managing the netapp).

We are not going to be doing backups on any systems on the netapp, merely relying on replication/snapshots. So this may be dev/qa stuff. Prod will go on our hitachi's and compellent.

So what I am concerned about is the dirty buffer issue on the os's. If a Netapp snaps at Time=0, during that time there will of course be data in the guest ram that is not yet committed to disk, or maybe not flushed from the esx host memory yet--the netapp snap will miss those transactions. So I am worried that if we have to recover a vm from a netapp snap it may be corrupted because of not getting a consistent state.

Would taking an esx snapshot, and then having netapp snap that ensure consistency?

I hope I have explained this properly what my concerns are. Thankyou.

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3 Replies
dustinn3
Contributor
Contributor

We are looking to do the same by adding another Netapp at a remote location. If you have licensing for the Netapp snapshot agents it should ensure consistent snapshots. We're still backing up with backup exec for now, but I use SMVI to backup the vm's as well. I've tried restoring a few snaps on test systems and it seemed to work just fine.

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FranckRookie
Leadership
Leadership

Hi Jedijeff,

If you want to insure the consistency of your NetApp Snapshots, you need to put your VMs into VMware Snapshot mode first. This freezes the disk activity during NetApp operation. In fact, that is exactly what SMVI does: it organizes the different snapshot executions to have a consistent data in its snapshot area.

Good luck.

Regards

Franck

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jsykora
Enthusiast
Enthusiast

If you want to use NetApp Snapshots and SnapMirror replication as your backup I would strongly suggest the SnapManager for Virtual Infrastructure license (SMVI) so you get application consistent (like you gracefully shut down the VM) snapshots on your storage. If you're just using the NetApp Snapshots and SnapMirror replication as a DR solution, then it might not be as critical as you'll generally get a crash consistent (like you pulled the power cord out of the box) snapshot. Please keep in mind that application consistent snapshots are really only possible if your app is VSS-aware without some sort of special scripting inside the VMware Tools.

Also if you are really good at Powershell scripting you could probably toss something together using both the VMware Powershell APIs and the NetApp Powershell APIs that would find all the VMs resident on a NetApp Volume/LUN, quieces all those VMs by taking a VMware Snapshot (with memory), and then once all VMware snapshots are taken perform a NetApp snapshot, then release the VMware snapshots, maybe run an ASIS operation on the NetApp volume, and then kick off a SnapMirror schedule from the remote NetApp filer.

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