[OmniOS-discuss] Auto snapshots?

[Theo Schlossnagle]

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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>>
>
>
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-- 

Theo Schlossnagle

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