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From Logan Barfield <lbarfi...@tqhosting.com>
Subject Re: Your thoughts on using Primary Storage for keeping snapshots
Date Mon, 16 Feb 2015 18:02:19 GMT
Hi Mike,

I agree it is a general CloudStack issue that can be addressed across
multiple primary storage options.  It's a two stage issue since some
changes will need to be implemented to support these features across
the board, and others will need to be made to each storage option.

It would be nice to see a single issue opened to cover this across all
available storage options.  Maybe have a community vote on what
support they want to see, and not consider the feature complete until
all of the desired options are implemented?  That would slow down
development for sure, but it would ensure that it was supported where
it needs to be.

Thank You,

Logan Barfield
Tranquil Hosting


On Mon, Feb 16, 2015 at 12:42 PM, Mike Tutkowski
<mike.tutkowski@solidfire.com> wrote:
> For example, Punith from CloudByte sent out an e-mail yesterday that was
> very similar to this thread, but he was wondering how to implement such a
> concept on his company's SAN technology.
>
> On Mon, Feb 16, 2015 at 10:40 AM, Mike Tutkowski <
> mike.tutkowski@solidfire.com> wrote:
>
>> Yeah, I think it's a similar concept, though.
>>
>> You would want to take snapshots on Ceph (or some other backend system
>> that acts as primary storage) instead of copying data to secondary storage
>> and calling it a snapshot.
>>
>> For Ceph or any other backend system like that, the idea is to speed up
>> snapshots by not requiring CPU cycles on the front end or network bandwidth
>> to transfer the data.
>>
>> In that sense, this is a general-purpose CloudStack problem and it appears
>> you are intending on discussing only the Ceph implementation here, which is
>> fine.
>>
>> On Mon, Feb 16, 2015 at 10:34 AM, Logan Barfield <lbarfield@tqhosting.com>
>> wrote:
>>
>>> Hi Mike,
>>>
>>> I think the interest in this issue is primarily for Ceph RBD, which
>>> doesn't use iSCSI or SAN concepts in general.  As well I believe RBD
>>> is only currently supported in KVM (and VMware?).  QEMU has native RBD
>>> support, so it attaches the devices directly to the VMs in question.
>>> It also natively supports snapshotting, which is what this discussion
>>> is about.
>>>
>>> Thank You,
>>>
>>> Logan Barfield
>>> Tranquil Hosting
>>>
>>>
>>> On Mon, Feb 16, 2015 at 11:46 AM, Mike Tutkowski
>>> <mike.tutkowski@solidfire.com> wrote:
>>> > I should have also commented on KVM (since that was the hypervisor
>>> called
>>> > out in the initial e-mail).
>>> >
>>> > In my situation, most of my customers use XenServer and/or ESXi, so KVM
>>> has
>>> > received the fewest of my cycles with regards to those three
>>> hypervisors.
>>> >
>>> > KVM, though, is actually the simplest hypervisor for which to implement
>>> > these changes (since I am using the iSCSI adapter of the KVM agent and
>>> it
>>> > just essentially passes my LUN to the VM in question).
>>> >
>>> > For KVM, there is no clustered file system applied to my backend LUN,
>>> so I
>>> > don't have to "worry" about that layer.
>>> >
>>> > I don't see any hurdles like *immutable* UUIDs of SRs and VDIs (such is
>>> the
>>> > case with XenServer) or having to re-signature anything (such is the
>>> case
>>> > with ESXi).
>>> >
>>> > On Mon, Feb 16, 2015 at 9:33 AM, Mike Tutkowski <
>>> > mike.tutkowski@solidfire.com> wrote:
>>> >
>>> >> I have been working on this on and off for a while now (as time
>>> permits).
>>> >>
>>> >> Here is an e-mail I sent to a customer of ours that helps describe
>>> some of
>>> >> the issues:
>>> >>
>>> >> *** Beginning of e-mail ***
>>> >>
>>> >> The main requests were around the following features:
>>> >>
>>> >> * The ability to leverage SolidFire snapshots.
>>> >>
>>> >> * The ability to create CloudStack templates from SolidFire snapshots.
>>> >>
>>> >> I had these on my roadmap, but bumped the priority up and began work
on
>>> >> them for the CS 4.6 release.
>>> >>
>>> >> During design, I realized there were issues with the way XenServer is
>>> >> architected that prevented me from directly using SolidFire snapshots.
>>> >>
>>> >> I could definitely take a SolidFire snapshot of a SolidFire volume,
but
>>> >> this snapshot would not be usable from XenServer if the original
>>> volume was
>>> >> still in use.
>>> >>
>>> >> Here is the gist of the problem:
>>> >>
>>> >> When XenServer leverages an iSCSI target such as a SolidFire volume,
it
>>> >> applies a clustered files system to it, which they call a storage
>>> >> repository (SR). An SR has an *immutable* UUID associated with it.
>>> >>
>>> >> The virtual volume (which a VM sees as a disk) is represented by a
>>> virtual
>>> >> disk image (VDI) in the SR. A VDI also has an *immutable* UUID
>>> associated
>>> >> with it.
>>> >>
>>> >> If I take a snapshot (or a clone) of the SolidFire volume and then
>>> later
>>> >> try to use that snapshot from XenServer, XenServer complains that the
>>> SR on
>>> >> the snapshot has a UUID that conflicts with an existing UUID.
>>> >>
>>> >> In other words, it is not possible to use the original SR and the
>>> snapshot
>>> >> of this SR from XenServer at the same time, which is critical in a
>>> cloud
>>> >> environment (to enable creating templates from snapshots).
>>> >>
>>> >> The way I have proposed circumventing this issue is not ideal, but
>>> >> technically works (this code is checked into the CS 4.6 branch):
>>> >>
>>> >> When the time comes to take a CloudStack snapshot of a CloudStack
>>> volume
>>> >> that is backed by SolidFire storage via the storage plug-in, the
>>> plug-in
>>> >> will create a new SolidFire volume with characteristics (size and IOPS)
>>> >> equal to those of the original volume.
>>> >>
>>> >> We then have XenServer attach to this new SolidFire volume, create a
>>> *new*
>>> >> SR on it, and then copy the VDI from the source SR to the destination
>>> SR
>>> >> (the new SR).
>>> >>
>>> >> This leads to us having a copy of the VDI (a "snapshot" of sorts), but
>>> it
>>> >> requires CPU cycles on the compute cluster as well as network
>>> bandwidth to
>>> >> write to the SAN (thus it is slower and more resource intensive than
a
>>> >> SolidFire snapshot).
>>> >>
>>> >> I spoke with Tim Mackey (who works on XenServer at Citrix) concerning
>>> this
>>> >> issue before and during the CloudStack Collaboration Conference in
>>> Budapest
>>> >> in November. He agreed that this is a legitimate issue with the way
>>> >> XenServer is designed and could not think of a way (other than what
I
>>> was
>>> >> doing) to get around it in current versions of XenServer.
>>> >>
>>> >> One thought is to have a feature added to XenServer that enables you
to
>>> >> change the UUID of an SR and of a VDI.
>>> >>
>>> >> If I could do that, then I could take a SolidFire snapshot of the
>>> >> SolidFire volume and issue commands to XenServer to have it change the
>>> >> UUIDs of the original SR and the original VDI. I could then recored
the
>>> >> necessary UUID info in the CS DB.
>>> >>
>>> >> *** End of e-mail ***
>>> >>
>>> >> I have since investigated this on ESXi.
>>> >>
>>> >> ESXi does have a way for us to "re-signature" a datastore, so backend
>>> >> snapshots can be taken and effectively used on this hypervisor.
>>> >>
>>> >> On Mon, Feb 16, 2015 at 8:19 AM, Logan Barfield <
>>> lbarfield@tqhosting.com>
>>> >> wrote:
>>> >>
>>> >>> I'm just going to stick with the qemu-img option change for RBD
for
>>> >>> now (which should cut snapshot time down drastically), and look
>>> >>> forward to this in the future.  I'd be happy to help get this moving,
>>> >>> but I'm not enough of a developer to lead the charge.
>>> >>>
>>> >>> As far as renaming goes, I agree that maybe backups isn't the right
>>> >>> word.  That being said calling a full-sized copy of a volume a
>>> >>> "snapshot" also isn't the right word.  Maybe "image" would be better?
>>> >>>
>>> >>> I've also got my reservations about "accounts" vs "users" (I think
>>> >>> "departments" and "accounts or users" respectively is less confusing),
>>> >>> but that's a different thread.
>>> >>>
>>> >>> Thank You,
>>> >>>
>>> >>> Logan Barfield
>>> >>> Tranquil Hosting
>>> >>>
>>> >>>
>>> >>> On Mon, Feb 16, 2015 at 10:04 AM, Wido den Hollander <wido@widodh.nl>
>>> >>> wrote:
>>> >>> >
>>> >>> >
>>> >>> > On 16-02-15 15:38, Logan Barfield wrote:
>>> >>> >> I like this idea a lot for Ceph RBD.  I do think there
should
>>> still be
>>> >>> >> support for copying snapshots to secondary storage as needed
(for
>>> >>> >> transfers between zones, etc.).  I really think that this
could be
>>> >>> >> part of a larger move to clarify the naming conventions
used for
>>> disk
>>> >>> >> operations.  Currently "Volume Snapshots" should probably
really be
>>> >>> >> called "Backups".  So having "snapshot" functionality,
and a
>>> "convert
>>> >>> >> snapshot to backup/template" would be a good move.
>>> >>> >>
>>> >>> >
>>> >>> > I fully agree that this would be a very great addition.
>>> >>> >
>>> >>> > I won't be able to work on this any time soon though.
>>> >>> >
>>> >>> > Wido
>>> >>> >
>>> >>> >> Thank You,
>>> >>> >>
>>> >>> >> Logan Barfield
>>> >>> >> Tranquil Hosting
>>> >>> >>
>>> >>> >>
>>> >>> >> On Mon, Feb 16, 2015 at 9:16 AM, Andrija Panic <
>>> >>> andrija.panic@gmail.com> wrote:
>>> >>> >>> BIG +1
>>> >>> >>>
>>> >>> >>> My team should submit some patch to ACS for better
KVM snapshots,
>>> >>> including
>>> >>> >>> whole VM snapshot etc...but it's too early to give
details...
>>> >>> >>> best
>>> >>> >>>
>>> >>> >>> On 16 February 2015 at 13:01, Andrei Mikhailovsky <
>>> andrei@arhont.com>
>>> >>> wrote:
>>> >>> >>>
>>> >>> >>>> Hello guys,
>>> >>> >>>>
>>> >>> >>>> I was hoping to have some feedback from the community
on the
>>> subject
>>> >>> of
>>> >>> >>>> having an ability to keep snapshots on the primary
storage where
>>> it
>>> >>> is
>>> >>> >>>> supported by the storage backend.
>>> >>> >>>>
>>> >>> >>>> The idea behind this functionality is to improve
how snapshots
>>> are
>>> >>> >>>> currently handled on KVM hypervisors with Ceph
primary storage.
>>> At
>>> >>> the
>>> >>> >>>> moment, the snapshots are taken on the primary
storage and being
>>> >>> copied to
>>> >>> >>>> the secondary storage. This method is very slow
and inefficient
>>> even
>>> >>> on
>>> >>> >>>> small infrastructure. Even on medium deployments
using snapshots
>>> in
>>> >>> KVM
>>> >>> >>>> becomes nearly impossible. If you have tens or
hundreds
>>> concurrent
>>> >>> >>>> snapshots taking place you will have a bunch of
timeouts and
>>> errors,
>>> >>> your
>>> >>> >>>> network becomes clogged, etc. In addition, using
these snapshots
>>> for
>>> >>> >>>> creating new volumes or reverting back vms also
slow and
>>> >>> inefficient. As
>>> >>> >>>> above, when you have tens or hundreds concurrent
operations it
>>> will
>>> >>> not
>>> >>> >>>> succeed and you will have a majority of tasks with
errors or
>>> >>> timeouts.
>>> >>> >>>>
>>> >>> >>>> At the moment, taking a single snapshot of relatively
small
>>> volumes
>>> >>> (200GB
>>> >>> >>>> or 500GB for instance) takes tens if not hundreds
of minutes.
>>> Taking
>>> >>> a
>>> >>> >>>> snapshot of the same volume on ceph primary storage
takes a few
>>> >>> seconds at
>>> >>> >>>> most! Similarly, converting a snapshot to a volume
takes tens if
>>> not
>>> >>> >>>> hundreds of minutes when secondary storage is involved;
compared
>>> with
>>> >>> >>>> seconds if done directly on the primary storage.
>>> >>> >>>>
>>> >>> >>>> I suggest that the CloudStack should have the ability
to keep
>>> volume
>>> >>> >>>> snapshots on the primary storage where this is
supported by the
>>> >>> storage.
>>> >>> >>>> Perhaps having a per primary storage setting that
enables this
>>> >>> >>>> functionality. This will be beneficial for Ceph
primary storage
>>> on
>>> >>> KVM
>>> >>> >>>> hypervisors and perhaps on XenServer when Ceph
will be supported
>>> in
>>> >>> a near
>>> >>> >>>> future.
>>> >>> >>>>
>>> >>> >>>> This will greatly speed up the process of using
snapshots on KVM
>>> and
>>> >>> users
>>> >>> >>>> will actually start using snapshotting rather than
giving up with
>>> >>> >>>> frustration.
>>> >>> >>>>
>>> >>> >>>> I have opened the ticket CLOUDSTACK-8256, so please
cast your
>>> vote
>>> >>> if you
>>> >>> >>>> are in agreement.
>>> >>> >>>>
>>> >>> >>>> Thanks for your input
>>> >>> >>>>
>>> >>> >>>> Andrei
>>> >>> >>>>
>>> >>> >>>>
>>> >>> >>>>
>>> >>> >>>>
>>> >>> >>>>
>>> >>> >>>
>>> >>> >>>
>>> >>> >>> --
>>> >>> >>>
>>> >>> >>> Andrija Panić
>>> >>>
>>> >>
>>> >>
>>> >>
>>> >> --
>>> >> *Mike Tutkowski*
>>> >> *Senior CloudStack Developer, SolidFire Inc.*
>>> >> e: mike.tutkowski@solidfire.com
>>> >> o: 303.746.7302
>>> >> Advancing the way the world uses the cloud
>>> >> <http://solidfire.com/solution/overview/?video=play>*™*
>>> >>
>>> >
>>> >
>>> >
>>> > --
>>> > *Mike Tutkowski*
>>> > *Senior CloudStack Developer, SolidFire Inc.*
>>> > e: mike.tutkowski@solidfire.com
>>> > o: 303.746.7302
>>> > Advancing the way the world uses the cloud
>>> > <http://solidfire.com/solution/overview/?video=play>*™*
>>>
>>
>>
>>
>> --
>> *Mike Tutkowski*
>> *Senior CloudStack Developer, SolidFire Inc.*
>> e: mike.tutkowski@solidfire.com
>> o: 303.746.7302
>> Advancing the way the world uses the cloud
>> <http://solidfire.com/solution/overview/?video=play>*™*
>>
>
>
>
> --
> *Mike Tutkowski*
> *Senior CloudStack Developer, SolidFire Inc.*
> e: mike.tutkowski@solidfire.com
> o: 303.746.7302
> Advancing the way the world uses the cloud
> <http://solidfire.com/solution/overview/?video=play>*™*

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