Re: [Xen-users] xm migrate headache

[Maxim Doucet <maxim@xxxxxxxxxxxx>]

Rainer Sokoll a écrit :
> On Tue, Mar 03, 2009 at 06:57:28AM -0700, Nick Couchman wrote:
>
> [drbd in primary/primary]
>
> I was not really correct - there is no filesystem at all in my drbd
> devices:
>
> -------8<-------
> hosta:~ # fdisk -l /dev/drbd4
>
> Disk /dev/drbd4: 2147 MB, 2147381248 bytes
> 255 heads, 63 sectors/track, 261 cylinders
> Units = cylinders of 16065 * 512 = 8225280 bytes
> Disk identifier: 0x000d0023
>
>       Device Boot      Start         End      Blocks   Id  System
> /dev/drbd4p1               1          28      224878+  82  Linux swap / 
> Solaris
> /dev/drbd4p2              29         261     1871572+  83  Linux
> -------8<-------
>
> The same at hostb.
> So. my drbd devices contain partitions, and these partitions contain a
> filesystem (ext3 and swap, in my case)
>   
Maybe this setup falls into the one described in /etc/drbd.conf (from
the "disk" sub-section)?

    # In some special circumstances the device mapper stack manages to
    # pass BIOs to DRBD that violate the constraints that are set forth
    # by DRBD's merge_bvec() function and which have more than one bvec.
    # A known example is:
    # phys-disk -> DRBD -> LVM -> Xen -> missaligned partition (63) ->
DomU FS
    # Then you might see "bio would need to, but cannot, be split:" in
    # the Dom0's kernel log.
    # The best workaround is to proper align the partition within
    # the VM (E.g. start it at sector 1024). (Costs 480 KiByte of storage)
    # Unfortunately the default of most Linux partitioning tools is
    # to start the first partition at an odd number (63). Therefore
    # most distribution's install helpers for virtual linux machines will
    # end up with missaligned partitions.
    # The second best workaround is to limit DRBD's max bvecs per BIO
    # (= max-bio-bvecs) to 1. (Costs performance).
    # max-bio-bvecs 1;

Maybe you could try with the option "max-bio-bvecs 1;" as described...

-- 
Maxim Doucet (maxim@xxxxxxxxxxxx)
sys engineer @ la maison
+33 (0)1 41 12 2000
www.alamaison.fr


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