[Question] Using backend snapshots with a storage repository

[Question] Using backend snapshots with a storage repository

[Mike Tutkowski]

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Hi,

I'm a software engineer at a data-storage company in Boulder called
SolidFire.

I work on the Apache CloudStack project on behalf of my company to help
drive CloudStack's storage architecture forward.

I have a question with regards to storage repositories and backend (SAN, in
this case) snapshots.

If I have a storage repository on a LUN, I can take a snapshot of the LUN
using my company's snapshot technology.

A problem comes into play, however, when I try to attach this new LUN to
the same Xen cluster as the LUN it is a snapshot of.

Xen does not like the fact that both SRs have the same UUID (and, in fact,
VDIs in each SR have duplicate UUIDs).

It appears UUIDs are immutable, so I'm not sure how to cleanly get around
this problem.

Since I write code that supports multiple hypervisors in CloudStack, I also
came across this issue in ESXi.

Here is ESXi's solution:

https://pubs.vmware.com/vsphere-50/index.jsp?topic=%2Fcom.vmware.wssdk.pg.doc_50%2FPG_Ch8_Storage.10.9.html

At the time being, I cannot use a backend-snapshot mechanism for Xen. What
I do is create a new LUN, a new SR on this LUN, take a VM snapshot of the
VDI I want that's on the source SR, then copy the VM snapshot of the VDI to
the new SR (then delete the VM snapshot of the VDI on the source SR).

Even though our SAN de-duplicates the storage blocks (so not a lot of new
data is written to the SAN), this workaround takes up front-end CPU cycles
and network bandwidth (and a noticeable amount time compared to backend
snapshots, which can be almost instantaneous).

What do you recommend?

Thanks!

-- 
*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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Re: [Question] Using backend snapshots with a storage repository

[Ian Campbell]

Hi Mike,

On Tue, 2015-01-27 at 14:47 -0700, Mike Tutkowski wrote:

> Xen does not like the fact that both SRs have the same UUID (and, in
> fact, VDIs in each SR have duplicate UUIDs).

The use of this terminology suggests that you are using XenServer rather
than the upstream version of Xen which is what is supported on this
list.

Support for XenServer is available either from the xenserver community
resources (lists, forums etc) over at www.xenserver.org or from your
Citrix support rep, if you have one.

Thanks,
Ian.

Re: [Question] Using backend snapshots with a storage repository

[Mike Tutkowski]

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Ah, sorry about that, wrong list indeed.

On Wednesday, January 28, 2015, Ian Campbell <Ian.Campbell@citrix.com>
wrote:

> Hi Mike,
>
> On Tue, 2015-01-27 at 14:47 -0700, Mike Tutkowski wrote:
>
> > Xen does not like the fact that both SRs have the same UUID (and, in
> > fact, VDIs in each SR have duplicate UUIDs).
>
> The use of this terminology suggests that you are using XenServer rather
> than the upstream version of Xen which is what is supported on this
> list.
>
> Support for XenServer is available either from the xenserver community
> resources (lists, forums etc) over at www.xenserver.org or from your
> Citrix support rep, if you have one.
>
> Thanks,
> Ian.
>
>
>

-- 
*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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