Xen users - Oct 2010 - Xen domU crashes accessing to drbd disk if using maxmem.

Hello all,

I''ve just installed a new dom0 with openSUSE 11.3 (x86_64)
and I''m seeing domUs crashes when reading from disks.
The problem occours when in domU configuration I use

memory=1024
maxmem=2048

My setup is DRBD on LVM on Software RAID 10 and drbd
devices are used as disks for domUs, using

phy:/dev/drbd0,hda,w
phy:/dev/drbd1,hdb,w

The domU in test is HVM, I''m using the openSUSE 11.3 rescue
system for testing. drbd0 is 300Gb and is partitioned this way:

      Device Boot      Start         End      Blocks   Id  System
/dev/drbd0p1            2048    31459327    15728640   83  Linux
/dev/drbd0p2        31459328   614381175   291460924   83  Linux

On dom0 I can successfully do

dd if=/dev/drbd0 of=/dev/null bs=1M
(~185 MB/s speed, if it can be useful)

the same (similar) command in domU on /dev/sda (dev/drbd0 as seen
by domU) causes domU to crash, but only if I start the domain using less
memory than maxmem. If I have memory=maxmem the disk read is ok
(~175MB/s speed).

I''ve found the problem trying to check the FS on /dev/sda2 (ReiserFS)
and then discovered that it''s relative to any "massive" disk
access I do.

In Xen logs:

[2010-10-04 15:34:55 5816] WARNING (XendDomainInfo:2106) Domain has crashed: 
name=mydomu id=15.
[2010-10-04 15:34:55 5816] DEBUG (XendDomainInfo:3115) 
XendDomainInfo.destroy: domid=15
[2010-10-04 15:34:56 5816] DEBUG (XendDomainInfo:2450) Destroying device 
model
[2010-10-04 15:34:57 5816] INFO (image:626) mydomu device model terminated
[2010-10-04 15:34:57 5816] DEBUG (XendDomainInfo:2457) Releasing devices

I''ve tried using openSUSE 11.2 and 11.3 boot disks and a trk disk
to do the ''dd'' or the ''reiserfsck'' having
identical results (domU crash).
Dom0 kernel is 2.6.34.7-0.3-xen, one of tested kernel is 2.6.34-12-default
(openSUSE rescue disk).

Some hint about this? What am I missing?

Thanks,
Valerio Granato


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---- Original Message ----
From: "Valerio Granato" <contact@livenet.it>
To: "Xen Users" <xen-users@lists.xensource.com>
Sent: Monday, October 04, 2010 5:01 PM
Subject: [Xen-users] Xen domU crashes accessing to drbd disk if using
maxmem. 
> The problem occours when in domU configuration I use
> 
> memory=1024
> maxmem=2048
>
> The domU in test is HVM
That''s the problem: maxmem AND hvm, when I run PV kernel the domU
works well.

On start xen allocates "memory" and hvm domU sees
''maxmem'',
I don''t know if it''s my fault in reading docs or it''s
a bug.

Valerio

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