WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-users

Re: [Xen-users] Consistent VM image backups

To: Simon Hobson <linux@xxxxxxxxxxxxxxxx>
Subject: Re: [Xen-users] Consistent VM image backups
From: Bart Coninckx <bart.coninckx@xxxxxxxxxx>
Date: Sun, 30 Jan 2011 00:05:29 +0100
Cc: xen-users@xxxxxxxxxxxxxxxxxxx
Delivery-date: Sat, 29 Jan 2011 15:08:51 -0800
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <p06240876c9682f639e90@xxxxxxxxxxxxxxxxxxxxxx>
List-help: <mailto:xen-users-request@lists.xensource.com?subject=help>
List-id: Xen user discussion <xen-users.lists.xensource.com>
List-post: <mailto:xen-users@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/mailman/listinfo/xen-users>, <mailto:xen-users-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-users>, <mailto:xen-users-request@lists.xensource.com?subject=unsubscribe>
References: <AANLkTikQug9MeVX4vskCfd5pc5sh0oC7NV6nic4+2BAW@xxxxxxxxxxxxxx> <AANLkTikkuHnQ25zDCsw6s53gM-KaHJh7G7hZ76ykmBVH@xxxxxxxxxxxxxx> <AANLkTi=Kvuh9Xq0MABHdVwMbB6=pctHdm0CKLJs1za+s@xxxxxxxxxxxxxx> <p06240876c9682f639e90@xxxxxxxxxxxxxxxxxxxxxx>
Sender: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.16) Gecko/20101125 SUSE/3.0.11 Thunderbird/3.0.11
On 01/28/11 09:36, Simon Hobson wrote:
> Mike Sun wrote:
>> I'm not worried about uncommitted data from the guest OS... I'm
>> capturing all of the domU memory state as well, so I guess I should be
>> more clear that I'm not looking for truly "consistent" disk image... I
>> just want to make sure that the virtual disk state is always synced to
>> the actual backing file.
>
> As long as you pause the guest and snapshot BOTH it's disk and machine
> state at the same instant (relative to guest operations) then between
> them you will have a consistent backup. BUT the ONLY way to use that
> backup is to restore both the disk image AND machine state and unpause
> the guest from that state. Any attempt to read the filesystem directly
> will result in reading dirty data which would be analogous to having
> pulled the power plug on the guest at the instant the snapshot was taken.
>
> Any uncommitted writes in the guest will be captured by the guest
> machine state, any uncommitted write in the host OS will be read as
> they would for any other write - as in a read of the file will use any
> dirty data waiting in the write cash rather than reading what is now
> invalid data from disk.
>
isn't pausing and saving the machine state actually the same as saving
the machine (xm save)?

B.



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