Re: [Xen-users] Storage alternatives

[Jan Marquardt <jm@xxxxxxxxxxx>]

> IOW: the iSCSI initiator and RAID (i guess it's RAID1) should be on
> Dom0, and the DomU configs should refer the resultant blockdevices.
This is one solution we are discussing at the moment, but I think it 
would be a lot smarter to get the raid functionality on a layer between 
 the harddisks and the iscsi targets as adviced by Nathan.
> Agreed.  You could even potentially move the mirroring down to the
> storage nodes (mirrored nbd/etc. devices) and HA the iSCSI target
> service itself to reduce dom0's work, although that would depend on you
> being comfortable with iSCSI moving around during a storage node
> failure, which may be a risk factor.
I think that we would have to reboot each domU in this case after a 
failure, isn't it? The goal is to have domUs which would not be affected 
by failure of one storage servers.
> If you have a storage node go offline in your current configuration for any 
> real length of time, when it becomes available again, all of the nodes will 
> begin to resync the array simultaneously.  With a single DomU, you'll just 
> consume the vast majority of either your Disk IO or Network IO.  However, 
> if you had a dozen guests, and they all start to rebuild their RAID1s from 
> the same source SAN to the same destination SAN, through the same network 
> link (in and out), at the same time, things are probably going to grind to 
> an absolute halt.
This is of course also one reason why I want to change the current setup.

> Abstract your disks and iscsi exports; then use ZFS on two pools this will
> minimize the administration. 
ZFS seems to be very nice, but sadly we are not using Solaris and don't 
want to use it with FUSE under Linux. Nevertheless does anyone use ZFS 
under Linux and can share his/her experiences?
Regards,

Jan


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