Re: [Xen-users] software raid (mdadm) with a local partition and a nbd device.

[Morten Bøgeskov <xen-users@xxxxxxxxxxxxxxxxxx>]

Hi

I've previously made a redundant iscsi-target with this:  
http://www.drbd.org/ because-i-could(tm). I didn't really have any  
useful reason (and both ran inside domU's on the same machine), but  
after some fiddling I got it up and running.
I don't recall if I ran LVM on the iscsi-target  
(http://iscsitarget.sourceforge.net/) side or the iscsi-client  
(http://www.open-iscsi.org/) side (client side I think), but it should  
be doable at both ends.
If you insist on running nbd I don't see why that shouldn't work. And  
you could run directly on the /dev/rdbdX, if you use your xen-machine  
as one of the drbd servers.
Yours
 Bøgeskov

Quoting Tomoki Taniguchi <tomoki.taniguchi@xxxxxxxxx>:

> I have a Fileserver serving out LVM partitions as domU disks
> using nbd. but since the file server is not redundant, I still
> have a single point of failure.  So if my Fileserver crashes,
> all my domUs on various dom0s will crash all at once.
>
> I want to avoid this situation.  I am thinking maybe I could
> alleviate this problem by setting up the nbd device with a local LVM
> lv partition
> as a raid 1 device.  that way if the fileserver fails and the nbd
> device becomes unavailable,
> then the domUs will keep writing to the local LV partition until the
> ndb device is back online
> and caches up.
>
> Is this possible?
>
> in the case this dom0 fails, start the domU on another dom0 and have
> the raid 1 catch up
> on that machine using the nbd device ?
>
> TIA,
> Tomoki
>
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