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Re: [Xen-users] Expanding a virtual block device

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Subject: Re: [Xen-users] Expanding a virtual block device
From: Vivien Bernet-Rollande <vivien.bernet-rollande@xxxxxxxxxxxxxxxxx>
Date: Mon, 02 May 2011 14:42:26 +0200
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I tried this and it's actually not a Xen issue. A resized volume in dom0
(even on DRBD :) ) is noticed by the domU.
So if your disk was 100G before and you add another 100G, fdisk(in domU)
will report a 200G disk after the resize in dom0.

This is interesting, as it is not the behaviour I have observed.

Let's check the disk (in dom0) at the start :
> x1:/home/vbernetr# blockdev --getsize64 /dev/sdc
> 42954915840

And in the domU :
> root@x-debian:~# blockdev --getsize64 /dev/xvdd
> 42954915840

Now I resize the iSCSI Lun :
> group01> volume select voltest01 size 70G

On the dom0, I rescan the connected targets, and check the size of the device :
> x1:/home/vbernetr# iscsiadm -m node -R
> x1:/home/vbernetr# blockdev --getsize64 /dev/sdc
> 75167170560

However, in domU, I still have the old size :
> root@x-debian:~# blockdev --getsize64 /dev/xvdd
> 42954915840

After a reboot domU sees the correct size.
> root@x-debian:~# blockdev --getsize64 /dev/xvdd
> 75167170560

Are you sure the experience you are describing happens without a reboot ? And if so, how are your virtual block devices configured ? Are you using "phy", "file", "tap:aio", or something else ?

Vivien Bernet-Rollande
Systems&  Networking Engineer
Alter Way Hosting

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