[OmniOS-discuss] Auto snapshots?

[Nicholas George]

If you have VMware Tools running on the VM(s), you can use the command line
api or the vSphere web service api to request that the VM is quiesced and
snapshotted, then take a snapshot of the ZFS storage. That should get you a
snapshot that is more than just crash-consistent.


On Tue, Apr 23, 2013 at 12:55 PM, Basil Crow <basil.crow at delphix.com> wrote:

> On Tue, Apr 23, 2013 at 7:40 AM, Eric Sproul <esproul at omniti.com> wrote:
> > But beyond those specifics, in the case where ZFS is providing a
> > backing store for what are seen as block devices by the ESXi guests,
> > you probably don't want blind ZFS snapshotting for the simple reason
> > that ZFS alone cannot ensure that the on-disk state of a given virtual
> > disk is consistent from the guest's viewpoint.  ZFS will happily
> > snapshot the filesystem on which the virtual disk file resides, but if
> > there are in-flight transactions in the guest to the filesystem backed
> > by that virtual disk file, the state represented by the snapshot may
> > be inconsistent.  You need some way to coordinate quiescing the guests
> > whose storage sits on the filesystem you want to snapshot, to make
> > sure their buffer caches are flushed out prior to the snapshot.  Maybe
> > someone on the list who does this can pipe up with specific techniques
> > in the VMware universe.
>
> Here at Delphix, we attempt to sync pending I/O by running
> /usr/sbin/sync in the guest OS with VMware Tools before taking the
> snapshot. It works well enough for our use case.
>
> Basil
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