[Xen-users] xen: when devices go away...

[Steve Wray <steve.wray@xxxxxxxxx>]

Hi there,
I've been experimenting with iscsi and xen and have found an interesting
behavior.

I'd reasoned that using iscsi volumes as devices in a software RAID1
configuration would be a Good Idea since when one of the iscsi servers
goes away the filesystem is stable.

I have a dom0 which has access to two iscsi volumes on two seperate
iscsi target servers.

I configure a domU with these two iscsi targets as its block devices, ie:

disk = [ 'phy:iscsi/iqn.2006-12.server1:raid/lun0/part,sda1,w',
        'phy:iscsi/iqn.2006-12.server2:raid/lun0/part,sdb1,w' ]

root = "/dev/md0 ro"

This works in as much as the domU has root on a RAID1 md device and it
functions normally; until I shutdown one of the iscsi servers. At that
point the domU dies horribly. I see no messages on the domU console at
all and so far nothing on the dom0 console either.

Nothing in any of the logs. I also don't see anything noteworthy in xm
log nor xm dmesg when this happens; the domU becomes unresponsive and
has to be killed with xm destroy.

Am I expecting too much? Will xen just not cope when one of the block
devices handed out to a domU simply 'goes away'?


iscsi aside, what would xen be expected to do if you had two scsi
drives, sda and sdb, presented to a domU as vbd's and used by the domU
in a RAID1 array... ie what would xen do if one of those hard drives failed?



Thanks!


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