XCP: RFC: compressing VM exports by default

XCP: RFC: compressing VM exports by default

[Dave Scott]

Hi,

In XCP a VM "export" is a serialized VM, including metadata and usually raw disk blocks. The format is a very simple tar file (really stream) with an XML file at the front containing version information and metadata.

Unfortunately VM exports containing raw disk blocks can be very large and their size makes them difficult to store and distribute over the network. I propose to turn on compression by default by filtering the exports through gzip and to auto-detect both compressed and uncompressed exports on import.

I've written up my proposal on the wiki:

http://wiki.xensource.com/xenwiki/Compressing_VM_exports

One implication is that new (compressed) exports will fail to import on older servers. However (a) there's an easy workaround (gunzip); and (b) I think being able to import an old (uncompressed) export on a new server is more important than the other way around.

Comments appreciated!

Cheers,
Dave

Re: XCP: RFC: compressing VM exports by default

[David Markey]

[-- Attachment #1.1: Type: text/plain, Size: 1279 bytes --]

Hmm could increase Dom0 load during an export.

I think its a good idea overall however.

On 22 June 2010 15:08, Dave Scott <Dave.Scott@eu.citrix.com> wrote:

> Hi,
>
> In XCP a VM "export" is a serialized VM, including metadata and usually raw
> disk blocks. The format is a very simple tar file (really stream) with an
> XML file at the front containing version information and metadata.
>
> Unfortunately VM exports containing raw disk blocks can be very large and
> their size makes them difficult to store and distribute over the network. I
> propose to turn on compression by default by filtering the exports through
> gzip and to auto-detect both compressed and uncompressed exports on import.
>
> I've written up my proposal on the wiki:
>
> http://wiki.xensource.com/xenwiki/Compressing_VM_exports
>
> One implication is that new (compressed) exports will fail to import on
> older servers. However (a) there's an easy workaround (gunzip); and (b) I
> think being able to import an old (uncompressed) export on a new server is
> more important than the other way around.
>
> Comments appreciated!
>
> Cheers,
> Dave
>
>
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xensource.com
> http://lists.xensource.com/xen-devel
>

[-- Attachment #1.2: Type: text/html, Size: 1831 bytes --]

[-- Attachment #2: Type: text/plain, Size: 138 bytes --]

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xensource.com
http://lists.xensource.com/xen-devel

RE: XCP: RFC: compressing VM exports by default

[Dave Scott]

[-- Attachment #1.1: Type: text/plain, Size: 1665 bytes --]

Hi David,

I think you're right to worry about dom0 load. I've updated the proposal to make compression an explicit option.

Cheers,
Dave

From: David Markey [mailto:admin@dmarkey.com]
Sent: 22 June 2010 14:18
To: Dave Scott
Cc: xen-devel@lists.xensource.com
Subject: Re: [Xen-devel] XCP: RFC: compressing VM exports by default

Hmm could increase Dom0 load during an export.

I think its a good idea overall however.
On 22 June 2010 15:08, Dave Scott <Dave.Scott@eu.citrix.com<mailto:Dave.Scott@eu.citrix.com>> wrote:
Hi,

In XCP a VM "export" is a serialized VM, including metadata and usually raw disk blocks. The format is a very simple tar file (really stream) with an XML file at the front containing version information and metadata.

Unfortunately VM exports containing raw disk blocks can be very large and their size makes them difficult to store and distribute over the network. I propose to turn on compression by default by filtering the exports through gzip and to auto-detect both compressed and uncompressed exports on import.

I've written up my proposal on the wiki:

http://wiki.xensource.com/xenwiki/Compressing_VM_exports

One implication is that new (compressed) exports will fail to import on older servers. However (a) there's an easy workaround (gunzip); and (b) I think being able to import an old (uncompressed) export on a new server is more important than the other way around.

Comments appreciated!

Cheers,
Dave



_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xensource.com<mailto:Xen-devel@lists.xensource.com>
http://lists.xensource.com/xen-devel


[-- Attachment #1.2: Type: text/html, Size: 8104 bytes --]

[-- Attachment #2: Type: text/plain, Size: 138 bytes --]

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xensource.com
http://lists.xensource.com/xen-devel