VMware Cloud Community
GBromage
Expert
Expert
Jump to solution

DRS & VCB

Hi there!

I have a number of VI3 hosts in a cluster at a data center. They are managed by a VirtualCenter server at a remote location over a WAN link (at another data center). DRS is enabled on the cluster, and I have a local VCB proxy in the data center in question.

With VCB, (specifically vcbVmName) it can take up to 2 minutes to resolve a name: reference to the server's moref: via VirtualCenter. It's virtually instantaneous when I query the VI3 server directly. As such, I'm considering using VCB to mount all the virtual servers by talking to the VI3 hosts directly, not via VirtualCenter.

Since VirtualCenter won't be aware of the snapshotting or mounting operations, what will happen if DRS wants to migrate the server partway through the snapshot or mount operation?

I hope this information helps you. If it does, please consider awarding points with the 'Helpful' or 'Correct' buttons. If it doesn't help you, please ask for clarification!
Reply
0 Kudos
1 Solution

Accepted Solutions
ErMaC1
Expert
Expert
Jump to solution

The Vmotion "snapshots" are different than vcb snapshots - VMotion does everything in memory whereas regular snapshots use things like redo logs and such. Vmotion, for example, doesn't need to snapshot disks at all (because it's not changing the disk location), it's just doing a memory copy.

The only time you'd have a problem is if you're in the middle of creating or committing a snapshot and VirtualCenter starts a VMotion. If you VMotion after a snapshot has already been made, the commit-snapshot will fail, but that can be fixed manually later.

View solution in original post

Reply
0 Kudos
4 Replies
kix1979
Immortal
Immortal
Jump to solution

Even though the snapshot is created via the local host, it will eventually (usually pretty quickly) be updated in VC as well. DRS will still function even though a snapshot has been created, it's just a revert may fail. Works fine for me Smiley Happy

Thomas H. Bryant III
GBromage
Expert
Expert
Jump to solution

Silly me! I thought that the point of having backups is so that you can rely on them being workable. Smiley Happy

IIRC, VMotion works by taking a snapshot/journal of the memory state. So if the machine is already being snapshotted whilst the snapshot occurs (or is being partially transferred), couldn't it corrupt the memory contents?

I hope this information helps you. If it does, please consider awarding points with the 'Helpful' or 'Correct' buttons. If it doesn't help you, please ask for clarification!
Reply
0 Kudos
kix1979
Immortal
Immortal
Jump to solution

It's possible with or without a snapshot. I've had a VM die on a vMotion, but that was once out of thousands of times.

Thomas H. Bryant III
Reply
0 Kudos
ErMaC1
Expert
Expert
Jump to solution

The Vmotion "snapshots" are different than vcb snapshots - VMotion does everything in memory whereas regular snapshots use things like redo logs and such. Vmotion, for example, doesn't need to snapshot disks at all (because it's not changing the disk location), it's just doing a memory copy.

The only time you'd have a problem is if you're in the middle of creating or committing a snapshot and VirtualCenter starts a VMotion. If you VMotion after a snapshot has already been made, the commit-snapshot will fail, but that can be fixed manually later.

Reply
0 Kudos