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] Xen 2.0 and LVM

To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-users] Xen 2.0 and LVM
From: Mark Williamson <mark.williamson@xxxxxxxxxxxx>
Date: Fri, 15 Jul 2005 01:49:05 +0100
Cc: Michal Ludvig <michal@xxxxxxxx>
Delivery-date: Fri, 15 Jul 2005 00:42:25 +0000
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <42D4CEF8.6040002@xxxxxxxx>
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/cgi-bin/mailman/listinfo/xen-users>, <mailto:xen-users-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-users>, <mailto:xen-users-request@lists.xensource.com?subject=unsubscribe>
References: <42D4CEF8.6040002@xxxxxxxx>
Sender: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
User-agent: KMail/1.8.1
> my Linux Xen domU machine have its filesystems on LVM volumes provided
> by dom0. I wonder what's the overhead of doing this. In my understanding
> all disk access must go through dom0 because only that knows about the
> LVM layout. Is that correct?

Yes.  It's transparent to the guest how its data is being stored.

Block accesses will *always* have to go through dom0 unless you dedicate a 
disk controller to the guest and give it a separate set of physical disks.

> Now I'm lookig for a way to optimize the IO performance for domU:
> - Should I allocate more memory in dom0 for it's disk buffers? Are they
> involved at all?

You shouldn't have any performance probs.  LVM is an efficient backing storage 
for guest block devices, as are partitions and whole disks.  Using dom0 files 
as guest disk storage is inefficient and should be avoided on high-throughput 
systems.

> - Can I dedicate whole disks (hdb, hdc) to one domU and let it handle
> all disk access including LVM itself without involving dom0 at all?

You can give the guest a whole IDE controller and associated disks using the 
PCI virtualisation stuff if you really want to - I doubt it's worth it 
though.  You shouldn't be seeing much (any?) noticeable disk overhead for 
typical workloads.

HTH,
Mark

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

<Prev in Thread] Current Thread [Next in Thread>