Hi folks,
We have been experiencing a problem with our test bed for a while now, and were
hoping perhaps some of the expertise on this mailing list might be able to help
us find a solution.
We have a cluster of 7 KVM vms on a host. The host OS is Fedora 18, and the
guest OS is Centos 6.4. Installed kvm/qemu/kernel packages are as follows:
qemu-system-x86-1.2.2-11.fc18.x86_64
qemu-common-1.2.2-11.fc18.x86_64
qemu-img-1.2.2-11.fc18.x86_64
libvirt-daemon-driver-qemu-0.10.2.5-1.fc18.x86_64
qemu-kvm-1.2.2-11.fc18.x86_64
ipxe-roms-qemu-20120328-2.gitaac9718.fc18.noarch
kernel-3.9.4-200.fc18.x86_64
To 4 of the vms we have attached the same 5 lvs to be used as shared storage,
with definitions like the below (disk1-disk5):
<disk type='block' device='disk'>
<driver name='qemu' type='raw' />
<source dev='/dev/vg_00/disk1'/>
<target dev='sda' bus='scsi'/>
<shareable/>
<serial>disk1</serial>
<alias name='scsi0-0-0'/>
<address type='drive' controller='0' bus='0' target='0' unit='0'/>
</disk>
Throughout the course of our automated test suite, our tests format the device
with an ext4 file system and then immediately mount the file system to write a
few files after the format completes. Most of the time this works great.
However, some small percentage of the time it is failing on the mount command
with "No such device".
Unable to mount /dev/disk/by-id/scsi-0QEMU_QEMU_HARDDISK_disk1: No such device
We know that the device does in fact exist and was operable, since the mkfs
command just had completed successfully and without error, so I am not sure why
suddenly it is returning "No such device" when trying to mount, and only a
small percentage of the time. To prove that the device is in fact there, we've
tried putting the mount into a retry-loop as a debug measure to show the device
is eventually there, and without fail in one of the loop iterations the mount
does complete successfully. It seems like there could possibly be some sort of
race between closing the device after the mkfs and quickly opening it again for
the mount?
We've reproduced this both with directly attached devices, as above, as well as
with iscsi devices.
At this point I am pretty stumped how to even continue debugging this issue, so
help would be very much appreciated!
Thankful for any help,
Kelsey Prantis
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