Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
Sorry for the duplicate, a problem with my email client. Here, is a forwarded email from the xen-users mailing list where someone encountered the same problem. A workaround is given, and further testing is done so I can only recommend to read it. The forwarded mail (http://lists.xensource.com/archives/html/xen-users/2007-08/msg00375.html) : > On Tue, 14 Aug 2007, Maxim Doucet wrote: > >> I experience the following error messages when launching the virtual >> machine : >> *On dom0 : the physical server* (messages coming from dmesg) : >> drbd0: bio would need to, but cannot, be split: >> (vcnt=2,idx=0,size=2048,sector=126353855) >> drbd0: bio would need to, but cannot, be split: >> (vcnt=2,idx=0,size=2048,sector=126353855) > > We are using a nearly identical configuration and experienced the same > problem just today: > > LVM2 on DRBD under Xen 3.0.3 w/ DRBD 8.0.4 Using CentOS5 on x86_64 > dom0 kernel 2.6.18-8.1.8-el5xen > > The virtual machine is an FC6 x86_64 PV guest and gave similar guest > errors. > > The workaround we are using is to change > > disk = [ 'phy:/dev/vg-drbd/vm0,xvda,w' ] > to > disk = [ 'tap:aio:/dev/vg-drbd/vm0,xvda,w' ] > > This treats the underlying backing image as a file. This may have > some performance loss since it is not using direct device IO, but as > far as I can tell it is stable. Or at least, phy: fails miserably, > where tap:aio: works fine! > > This seems to indicate that its not an LVM+DRBD or Xen+LVM problem, > but rather a Xen+LVM+DRBD using phy: problem. I tested to see if Xen > liked running LVM on a loopback device and loading a VM off it using > phy: (see below). It worked fine, which makes me think this is more > of a drbd issue than a Xen or LVM issue. > > If you are on the DRBD list, please cross-post this (as I am not) > since it is probably relevant. > > -Eric > > > ============== Xen+LVM+loop test: > > # dd if=/dev/zero bs=1G seek=32 count=1 of=/tmp/testimage > # losetup /dev/loop0 /tmp/testimage > # pvcreate /dev/loop0 > # vgcreate vg-loop /dev/loop0 > # pvscan > [...] > PV /dev/loop0 VG vg-loop lvm2 [11.00 GB / 6.99 GB free] > [...] > # lvcreate -n testvm -l 1025 vg-loop > > # lvascan > [...] > ACTIVE '/dev/vg-loop/testvm' [4.00 GB] inherit > [...] > > # ls -l > -rwxr-xr-x 1 root root 4294967297 Jul 23 16:22 disk0 > # dd if=disk0 bs=4M of=/dev/vg-loop/testvm > 1024+1 records in > 1024+1 records out > 4294967297 bytes (4.3 GB) copied, 396.227 seconds, 10.8 MB/s > -- Maxim Doucet - www.alamaison.fr sys admin @ la maison