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/
Home Products Support Community News


Re: [Xen-users] Re: Cannot boot with LVM inside Xen DomU

To: Prakhar Srivastava <prakhar.apj@xxxxxxxxx>
Subject: Re: [Xen-users] Re: Cannot boot with LVM inside Xen DomU
From: Oliver Wilcock <oliver@xxxxxxx>
Date: Sun, 17 Jul 2011 07:11:12 -0400
Cc: xen-users@xxxxxxxxxxxxxxxxxxx
Delivery-date: Sun, 17 Jul 2011 04:12:30 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <CAF+Dr+t6=0QYgKYS7tt4ZAnSr_AxpPdhgdidCRu4s0cny2pd3w@xxxxxxxxxxxxxx>
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: <20110710190309.D4E6240E96A3@xxxxxxxxxxxxxx> <76ec3df15cb1b4f87e4b98d7e1644164.squirrel@xxxxxxxxxxxxxx> <CAF+Dr+t6=0QYgKYS7tt4ZAnSr_AxpPdhgdidCRu4s0cny2pd3w@xxxxxxxxxxxxxx>
Sender: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
User-agent: Mozilla/5.0 (Windows NT 6.0; rv:5.0) Gecko/20110624 Thunderbird/5.0
Sorry about the late reply.

Resizing of the root disk.  Here are some thoughts:
I previously shared that you may run into trouble when upgrading if the root (/) is the entire disk. In my experience the SUSE installer was confused (it couldn't find the existing installation) and had to be tricked. Consequently I now put root on /dev/xvda1. It doesn't sound right that you can resize with xm block-attach. You may want to re-read whatever you are referring to. Why would you need to make your root disk bigger? It is probably smarter to put the data that grows on separate LVM backed storage. Perhaps you need to assign separate LVs to /home /var /opt. For relatively simple guests I would typically create an LV for swap, var and home and mount those as disks (phy:/dev/raid10x6/guestservername-home,xvdc,w). You can do online expansion of the LV which appears as a larger xvdc device.
In dom0: lvresize -L?GB /dev/raid10x6/guestservername-home

Performance penalty of nested LVM: I'm sure there is an impact (a few percent probably, I've never measured it). You might still want to do it though. I've done it once for the ability to create LV snapshots inside the guest as part of the backup strategy. I didn't do it on root (/) though. Just the mount points where I kept the databases and log files.

On 2011-07-11 14:47, Prakhar Srivastava wrote:

I have one more query. As stated by Fazar in his last reply,
Redhat/CentOS DomU have by default LVM within which allows them to
increase the root disk online by xm block-attach command. However, I
have read in one of the Xen list discussion that using LVM as DomU
backend and also within DomU is not a great idea in terms of
performance. I want to have a similar kind of setup and believe that
having the flexibility of resizing root disk online is a great plus in a
virtualized environment. What are your thoughts on this ??


Xen-users mailing list

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