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From Mike Tutkowski <mike.tutkow...@solidfire.com>
Subject Re: [PROPOSAL] ROOT volume detach - feature for CS 4.5
Date Fri, 28 Mar 2014 04:40:55 GMT
Hi Alena,

I was wondering if you've taken "managed" storage into consideration for
this?

If you're unfamiliar with it, managed storage is named as such because
CloudStack manages it on behalf of the admin (ex. dynamically creating SRs
as needed).

For example, when I add primary storage to CloudStack that is based on the
SolidFire SAN, I use the SolidFire plug-in, which is an example of managed
storage.

In this case, the primary storage represents a SAN as opposed to a
preallocated volume.

When the time comes to, say, attach a data disk to a VM for the first time,
the SolidFire plug-in goes off to its SAN and dynamically creates a new
volume on it (with the appropriate size and IOPS requirements).

CloudStack has logic that recognizes managed storage.

For example, for XenServer, its logic has been augmented to automatically
create an SR based on the iSCSI target that was created on the SAN and to
create a VDI within it that is attached to the VM in question.

The big takeaway is that each CloudStack volume here will be associated
with a unique volume on a SAN and consumed as an SR (XenServer) or
datastore (ESX) (KVM handles this differently). In this situation, there is
a 1:1 mapping between a SAN volume and an SR. No other VDIs are stored on
the SR except for the one representing this one CloudStack volume.

That being the case, I was wondering what you thought of this with regards
to your root-volume-detach feature?

If we don't want to look into this for 4.5, it might be best to simply fail
to detach a root volume from a VM if the volume is based on managed storage
or to fail to attach a bootable volume to a VM if it is based on managed
storage.

Talk to you later,
Mike


On Tue, Mar 25, 2014 at 1:24 PM, Alena Prokharchyk <
Alena.Prokharchyk@citrix.com> wrote:

> Mike,
>
> Volume has a template_id referencing vm_template table. Vm_template has
> bootable flag, so we will derive information from there.
> And sure, this information will not change if the root disk is detached.
>
> On 3/25/14, 12:18 PM, "Mike Tutkowski" <mike.tutkowski@solidfire.com>
> wrote:
>
> >Hi Alena,
> >
> >I was wondering how we plan to keep track of the new "bootable" property?
> >When we create a VM, would we just mark its root disk as bootable and then
> >that property becomes immutable (for the upgrade case, all root disks
> >would
> >be marked as bootable)?
> >
> >I'm thinking we'd want to keep track of bootable disks even when there are
> >detached and turned into data disks. Is that what you had in mind?
> >
> >Thanks!
> >Mike
> >
> >
> >On Tue, Mar 25, 2014 at 12:20 PM, Alena Prokharchyk <
> >Alena.Prokharchyk@citrix.com> wrote:
> >
> >> Here is the link to the corresponding FS (placed in "4.5 Design
> >>documents"
> >> section)
> >>
> >>
> >>
> https://cwiki.apache.org/confluence/display/CLOUDSTACK/ROOT+volume+detach
> >>
> >> -Alena.
> >>
> >> From: Alena Prokharchyk <alena.prokharchyk@citrix.com<mailto:
> >> alena.prokharchyk@citrix.com>>
> >> Date: Monday, March 24, 2014 at 11:37 AM
> >> To: "dev@cloudstack.apache.org<mailto:dev@cloudstack.apache.org>" <
> >> dev@cloudstack.apache.org<mailto:dev@cloudstack.apache.org>>
> >> Subject: [PROPOSAL] ROOT volume detach - feature for CS 4.5
> >>
> >> I would like to propose a new feature for CS 4.5 - "ROOT volume detach"
> >>-
> >> that enables support for following use cases:
> >>
> >> 1) Replace current ROOT volume with the new one for  existing vm.
> >> 2) Case when ROOT volume of vm1 gets corrupted, and you want to attach
> >>it
> >> to vm2 to run the recovery utils on it. With current CS implemntation,
> >>you
> >> have to perform several steps - create snapshot of vm1's volume, create
> >> volume from snapshot, attach volume to the vm2. New implementation will
> >> merge it all to one step.
> >>
> >>
> >> With the planned implementation, once the ROOT volume is detached, it
> >>can
> >> be attached to any existing vm (with respect to Admin/Domain/Physical
> >> resources limitations), either as a DataDisk or a Root disk.
> >>
> >> Amazon EC2 already has this functionality in place, so I think CS would
> >> only benefit from having it. Storage experts (Edison, others) please
> >>raise
> >> your concerns if you have any, or if you see any potential problems with
> >> the planned implementation. And if anyone can think of other use cases
> >>this
> >> feature can possible solve, I would appreciate this input as well.
> >>
> >>
> >> Feature limitations:
> >>
> >> * ROOT volume can be detached only when vm is in Stopped state
> >> * CS will fail to start the vm not having a ROOT volume
> >>
> >> I will send out the link to the FS once I start getting feedback on the
> >> proposal.
> >>
> >> -Alena.
> >>
> >
> >
> >
> >--
> >*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>
> >*(tm)*
>
>


-- 
*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>
*(tm)*

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