[OmniOS-discuss] Auto snapshots?

[Eric Sproul]

Hi Dan,
First, welcome.  :)  Your question does come up from time to time.
There isn't a "standard zfs auto-snapshot service" outside of Oracle
Solaris.  That is, it's not a baked-in feature of ZFS, but a service
added on top.  Back in OpenSolaris there was Time Slider, but that was
a desktop-oriented feature with GNOME integration, and isn't suitable
for server deployments.

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.

Eric

On Tue, Apr 23, 2013 at 9:20 AM, Dan Swartzendruber <dswartz at druber.com> wrote:
>
> New to the list, so forgive me if this is an FAQ (I googled and turned up
> nothing.)  I just installed omnios as a ZFS virtual appliance serving up
> virtual disks to ESXi via NFS.  Working great.  Is there a way to install
> the standard zfs auto-snapshot service?  Thanks!
>
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