Xen users - Jan 2008 - CentOS 5.0 + xen-3.0.3 + drbd-8.0.6 + heartbeat-2.1.2 + lvm2-2.02 : bio would need to, but cannot, be ,split

Hello,

This message is posted on both the DRBD & Xen mailing lists, sorry for
duplicate ...

I have two test servers (phys1 and phys2) under CentOS 5.0 as said in 
subject, I try to use virtual machines with xen using lvm above drbd and 
managed between the two hosts by heartbeat. I can only use one network 
interface on each host.
* I installed my two Dom0s on each server.
* I create LVM partition with fdisk and configure it for drbd :
global {    usage-count no; }
resource vm2 {
        protocol C;
        handlers { # this values are for testing
                pri-on-incon-degr "echo ''DRBD: primary requested
but
inconsistent!'' | wall; sleep 300000";
                pri-lost-after-sb "echo ''DRBD: primary lost after
Speed
Brain!'' | wall; sleep 300000";
                local-io-error "echo ''DRBD: local i/o
error!'' | wall;
sleep 300000";
        }
        startup { wfc-timeout        0;  degr-wfc-timeout   120;     }
        disk {on-io-error detach;        }
        net { cram-hmac-alg "sha1";  shared-secret
"*********";
after-sb-0pri discard-younger-primary;   
               after-sb-1pri consensus;    after-sb-2pri disconnect;  }
        syncer {rate   10M; }
        on phys1 {     device /dev/drbd1;  disk /dev/sda4;   address 
192.268.21.1:7788;  meta-disk internal;        }
        on phys2 {    device /dev/drbd1;   disk /dev/sda4;  address 
192.168.21.2:7788;   meta-disk internal;        }
}

* modifyinf /etc/lvm/lvm.conf
 filter = [ "r|/dev/sda4|", "a|/dev/drbd1|" ]
* pvcreate /dev/drbd1
* vgcreate VGxen /dev/drbd1
* lvcreate -L 10000 -n vm2 VGxen
* lvchange -a y /dev/VGxen/vm2
* While installing vm2 with virt-manager and while rebooting vm2 I can see 

- in messages on phys 1 :
Jan 22 17:02:46 phys1 kernel: drbd3: bio would need to, but cannot, be 
split: (vcnt=8,idx=0,size=4096,sector=13113083)
Jan 22 17:02:46 phys1 kernel: drbd3: bio would need to, but cannot, be 
split: (vcnt=8,idx=0,size=4096,sector=13113149)
Jan 22 17:02:46 phys1 kernel: drbd3: bio would need to, but cannot, be 
split: (vcnt=8,idx=0,size=4096,sector=13113215)

- on console on vm2 :
Buffer I/O error on device xvda2, logical block 0
Buffer I/O error on device xvda2, logical block 1
Buffer I/O error on device xvda2, logical block 2
Buffer I/O error on device xvda2, logical block 3
Buffer I/O error on device xvda2, logical block 4 
Buffer I/O error on device xvda2, logical block 5
Buffer I/O error on device xvda2, logical block 6
Buffer I/O error on device xvda2, logical block 7
Buffer I/O error on device xvda2, logical block 8
Buffer I/O error on device xvda2, logical block 9

and after that vm2 boot is ok.


Any idea on what can I do to make it work well ? I read on xen list
(http://lists.xensource.com/archives/html/xen-users/2007-08/msg00396.html)
that I should replace in /etc/xen/vm2
disk = [ "phy:/dev/mapper/VGxen-vm2,xvda,w" ]
by
disk = [ "tap:aio:/dev/mapper/VGxen-vm2,xvda,w" ]
what are the consequences ? is there any known problem with drbd or 
heartbeat or lvm ?

Thanks for any suggestions.

-- 
------------------------------------------------------------------------
JUAN Celine                        		         
Universite Paul Sabatier
CICT                              		     
31062 Toulouse Cedex 9 
FRANCE             
------------------------------------------------------------------------


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