# [OmniOS-discuss] Auto snapshots?

Theo Schlossnagle jesus at omniti.com
Tue Apr 23 18:06:32 EDT 2013

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    Wouldn't you want to snapshot the ZFS system and then quiesce and snapshot
    the VM?

    Step one: zfs snapshot; step two: make it not a lie.

    On Tue, Apr 23, 2013 at 5:48 PM, Nicholas George <headlesscow at gmail.com>wrote:

    > 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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    >> OmniOS-discuss at lists.omniti.com
    >> http://lists.omniti.com/mailman/listinfo/omnios-discuss
    >>
    >
    >
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    --

    Theo Schlossnagle

    http://omniti.com/is/theo-schlossnagle
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