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From Animesh Chaturvedi <animesh.chaturv...@citrix.com>
Subject RE: [MERGE] Support VM Snapshot
Date Fri, 08 Mar 2013 01:54:28 GMT
Folks following up on this thread looks like support for XenServer is still not settled. 

1. Mice can we make the feature configurable for each hypervisor to enable/disable the feature
2. Test the feature with XenServer thoroughly to check if Volume Snapshot is affected / degraded

Thanks
Animesh


> -----Original Message-----
> From: Anthony Xu [mailto:Xuefei.Xu@citrix.com]
> Sent: Friday, February 01, 2013 5:44 PM
> To: 'Mice Xia'; cloudstack-dev@incubator.apache.org; Alex Huang; Mice Xia
> Subject: RE: [MERGE] Support VM Snapshot
> 
> I see, snapshot manager detected the change in primary storage, and create
> a full snapshot instead, which is supposed to be a delta snapshot.
> 
> It doesn’t break volume snapshot function, but this degrades the volume
> snapshot performance.
> 
> 
> 
> This is just a simple test, it cannot prove there is no impact to volume
> snapshot.
> 
> I’m not sure what will happen if execute these two commands at the same
> time, is there any mechanism to sync/serialize these two operation?
> 
> I’m not sure if revert VM has impact to volume snapshot.
> 
> 
> 
> For now, it is better to have a global configuration to only choose one.
> 
> later, we may support both of them in one setup.
> 
> 
> 
> 
> 
> Anthony
> 
> 
> 
> 
> 
> 
> From: Mice Xia [mailto:mice_xia@tcloudcomputing.com]
> Sent: Friday, February 01, 2013 5:30 PM
> To: cloudstack-dev@incubator.apache.org; Alex Huang; Mice Xia; Anthony Xu
> Subject: 答复: [MERGE] Support VM Snapshot
> 
> 
> Anthony,
> 
> Thanks for your comments.
> 
> Tested on a datadisk with steps you provide on xenserver, all the files (test1,
> test2, test3) are present, the function is not affected.
> But as i have replied, volume snapshot (s2) is not a delta snapshot, it is a full
> one. Users need to be aware of this if they want to use both snapshots
> simultaneously.
> 
> Regards
> Mice
> 
> 
> -----Original Message-----
> From: Anthony Xu [mailto:Xuefei.Xu@citrix.com]
> Sent: 2013-2-2 (星期六) 4:05
> To: Alex Huang; Mice Xia; cloudstack-dev@incubator.apache.org
> Subject: RE: [MERGE] Support VM Snapshot
> 
> CS uses XenServer delta snapshot, snapshot manager records a VHD chain in
> snapshot DB for each volume. VM snapshot creation/revert also operate on
> volume snapshot, if snapshot manager doesn't know the VM snapshot ,
> volume snapshot might be broken.
> 
> 
> You can try following test,
> 
> 1. create a VM.
> 2. create empty file test1 inside this VM.
> 3. create a volume snapshot(s1)
> 4. create empty file test2 inside this VM 5. create a VM snapshot (vm1) 6.
> create empty file test3 inside this VM 7. create a volume snapshot (s2) 8.
> create a volume from snapshot (s2) 9. attach this volume to a VM 10. if one
> of test1, test2, test3 is missing in this volume, might mean volume snapshot
> is broken.
> 
> 
> It might be difficult to support both VM snapshot and volume snapshot in the
> same time for hypervisor which supports delta snapshot.
> Maybe we need to provide a zone level configuration for it, only one is
> supported in a zone, volume snapshot or vm snapshot.
> 
> 
> 
> Anthony
> 
> 
> 
> 
> 
> > -----Original Message-----
> > From: Alex Huang
> > Sent: Friday, February 01, 2013 10:54 AM
> > To: Mice Xia; cloudstack-dev@incubator.apache.org
> > Cc: Anthony Xu
> > Subject: RE: [MERGE] Support VM Snapshot
> >
> > Mice,
> >
> > Thanks!
> >
> > Anthony,
> >
> > Can you comment on whether VM Snapshot breaks volume snapshot?
> >
> > --Alex
> >
> > > -----Original Message-----
> > > From: Mice Xia [mailto:weiran.xia1@gmail.com]
> > > Sent: Friday, February 01, 2013 8:53 AM
> > > To: cloudstack-dev@incubator.apache.org; Alex Huang
> > > Subject: Re: [MERGE] Support VM Snapshot
> > >
> > > as Alex suggested
> > > updated vm-snapshot branch, commit ebca6890fd
> > >
> > > 1. remove snapshotting/revertting state from VM state machine
> > > 2  prevent VM state change if there are active vm snapshot tasks
> > > 3  change VMSnapshotService interface, except for ListVMSnapshotCmd,
> > > need some time to replace it in QueryService, maybe after merging to
> > > master
> > > 4  remove unused methods and fix some typos
> > >
> > > Regards
> > > Mice
> > >
> > > 2013/2/1 Mice Xia <mice_xia@tcloudcomputing.com>:
> > > > Hi, Alex,
> > > >
> > > > Thanks for your feedbacks, please see my comments inline.
> > > >
> > > > - VM states is designed for VM lifecycle.  Snapshot is not part of
> > VM life
> > > cycle so therefore the state should not be there.  I think it make
> > sense to add
> > > attributes to VM that says "Do Not Change State" and  who changed
> > > the
> > VM
> > > to that state.  Then virtualmachinemanager must obey that until the
> > external
> > > caller changes the attribute to now you can change state.  The would
> > make
> > > more sense and decouples snapshotting from vm lifecycle management.
> > > Snapshotting then has it's own state (which I see it does already).
> > If we want
> > > to reflect that a vm snapshot is being taken of a VM, that's a
> > function of the
> > > apiresponse module that gathers up everything about a vm but it
> > shouldn't
> > > be changed in the vm states.
> > > >
> > > > [mice] the reason that I added snapshotting/reverting state is
> > > > that
> > VM
> > > could be in suspend/pause state during snapshoting/reverting, which
> > is
> > > difficult to be categorized into existing states; and during the
> > process, VM
> > > should not be allowed to take any operations; and by adding new
> > states to
> > > VM, the implementation seems more 'natural' and only minimum codes
> > are
> > > changed to virtualmachinemanager.
> > > > Of course there are some other ways to prevent operations, such as
> > check
> > > if associated snapshots are in snapshotting/reverting states either
> > in each
> > > method (start/stop/migrate/delete...) or hook stateTransitTo(), but
> > in this
> > > way, it does not reflect VM's real state in hypervisor and more
> > existing codes
> > > will be touched.
> > > >
> > > > -  Does VM Revert operation work in the following way: Stop VM,
> > restore
> > > to snapshot, and run VM?  Shouldn't this be orchestration inside
> > snapshot
> > > manager?
> > > >
> > > > [mice] if a running VM is reverted to a memory enabled snapshot,
> > current
> > > implementation is running--> reverting-->running
> > > > If a stopped VM is reverted to memory disabled snapshot: stopped--
> > > >reverting->stopped
> > > > If a running VM is reverted to a memory disabled snapshot:
> > > > running-
> > -(Stop
> > > VM)-->stopped-->reverting--> stopped
> > > > If a stopped VM is reverted to a memory enabled snapshot:
> > > > stopped--
> > > (Start VM)-->running->reverting-->running
> > > >
> > > > These logics are implemented in snapshot manager.
> > > >
> > > > - Does VM snapshot interfere with volume snapshot?  Volume
> > > > snapshot
> > > today makes the assumption that it is the only code that's making
> > snapshots
> > > and can break if there are additional snapshots in between.  This is
> > bad
> > > design in volume snapshot but unfortunately that's how it's design.
> > > >
> > > > [mice] about volume snapshot, for xensever, if parent VHD cannot
> > > > be
> > > found, it will take a full volume snapshot (this indeed break
> > > current semantics but it still works)
> > > > For vmware, the volume snapshot is always a full one.
> > > >
> > > > - VMSnapshotService follows the other services in passing the cmds
> > to the
> > > service.  That's really a bad practice that we should stop.  Cmds
> > > are
> > really
> > > translations between over-the-wire api and java interface.  They
> > shouldn't
> > > have been passed to down to the java interface.
> > > > [
> > > > mice] I'll change it
> > > >
> > > > A small note: Would it be better to call it VM restore than VM
> > revert?
> > > Revert really should be RevertTo which I think is in the code but is
> > not
> > > consistent.  Some places it's just REVERT (for example, the event is
> > just
> > > revert).
> > > >
> > > > [mice] there is already RESTORE, which is restoring a destroyed VM
> > to
> > > stopped. RevertTo is fine with me.
> > > >
> > > > -Mice
> > > >
> > > >
> > > > -----Original Message-----
> > > > From: Alex Huang [mailto:Alex.Huang@citrix.com]
> > > > Sent: Friday, February 01, 2013 9:24 AM
> > > > To: CloudStack DeveloperList
> > > > Cc: Mice Xia
> > > > Subject: RE: [MERGE] Support VM Snapshot
> > > >
> > > > Hi Mice,
> > > >
> > > > Sorry it took so long to review this.  Wanted to as soon as I saw
> > it on the list
> > > but was sick and didn't get a chance.  In general, I think the code
> > is excellent.
> > > I'm impressed how much Cloudstack internal code in touch and how
> > > comfortable the changes look.  Nicely done!
> > > >
> > > > I have a few comments:
> > > > - VM states is designed for VM lifecycle.  Snapshot is not part of
> > VM life
> > > cycle so therefore the state should not be there.  I think it make
> > sense to add
> > > attributes to VM that says "Do Not Change State" and  who changed
> > > the
> > VM
> > > to that state.  Then virtualmachinemanager must obey that until the
> > external
> > > caller changes the attribute to now you can change state.  The would
> > make
> > > more sense and decouples snapshotting from vm lifecycle management.
> > > Snapshotting then has it's own state (which I see it does already).
> > If we want
> > > to reflect that a vm snapshot is being taken of a VM, that's a
> > function of the
> > > apiresponse module that gathers up everything about a vm but it
> > shouldn't
> > > be changed in the vm states.
> > > > -  Does VM Revert operation work in the following way: Stop VM,
> > restore
> > > to snapshot, and run VM?  Shouldn't this be orchestration inside
> > snapshot
> > > manager?
> > > > - Does VM snapshot interfere with volume snapshot?  Volume
> > > > snapshot
> > > today makes the assumption that it is the only code that's making
> > snapshots
> > > and can break if there are additional snapshots in between.  This is
> > bad
> > > design in volume snapshot but unfortunately that's how it's design.
> > > > - VMSnapshotService follows the other services in passing the cmds
> > to the
> > > service.  That's really a bad practice that we should stop.  Cmds
> > > are
> > really
> > > translations between over-the-wire api and java interface.  They
> > shouldn't
> > > have been passed to down to the java interface.
> > > >
> > > > A small note: Would it be better to call it VM restore than VM
> > revert?
> > > Revert really should be RevertTo which I think is in the code but is
> > not
> > > consistent.  Some places it's just REVERT (for example, the event is
> > just
> > > revert).
> > > >
> > > > --Alex
> > > >
> > > >> -----Original Message-----
> > > >> From: Chiradeep Vittal
> > > >> Sent: Wednesday, January 30, 2013 4:44 PM
> > > >> To: CloudStack DeveloperList
> > > >> Cc: Alex Huang
> > > >> Subject: Re: [MERGE] Support VM Snapshot
> > > >>
> > > >> Can we get Alex to review this? He is the designer of the state
> > machine.
> > > >>
> > > >> On 1/30/13 5:26 AM, "Murali Reddy" <Murali.Reddy@citrix.com>
> wrote:
> > > >>
> > > >> >On 30/01/13 2:24 PM, "Mice Xia" <mice_xia@tcloudcomputing.com>
> > > wrote:
> > > >> >
> > > >> >>Agreed.
> > > >> >>Adding VM states are likely to have some side-effects, but
for
> > > >> >>moveVMToUser case, does it explicitly reject other transient
> > states
> > > >> >>such as stating/stopping/migrating?
> > > >> >>
> > > >> >>-Mice
> > > >> >
> > > >> >No, it just accepts any state other than 'Running' (though it
> > should
> > > >> >have checked for the valid states in which VM can move to other
> > user).
> > > >> >
> > > >> >I am just saying, there could such VM state based assumptions,
> > you
> > > >> >might want to check.
> > > >> >
> > > >

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