What I'd like to do is something I know is possible with ENBD (Enhanced NBD) but the author is still tinkering with it so I'm not sure I entirely trust it. So I wondered if it's possible with iSCSI.
Basically, I want a hot-failover fileserver. Failover easy enough with VRRP component of keepalived. Mirroring data easy enough with rsync, but big performance hit syncing frequently; infrequent syncing bound to lead to loss of important changes.
So the basic idea is two servers each with one disk that is part of a networked software RAID array. Only the live server gets to read/write the array. Disk on live server dies, the server gives up the virtual IP. Live server dies, failover server mounts its disk locally. Some tinkering with keepalived scripting should take care of that. But is mdadm and iSCSI compatible in that scenario? Anyone know? Or willing to opine? If I had enough spare kit I'd just test it, but I don't have that luxury. :(
I've googled, but keep getting pages about a server with two disks in s/w raid being accessed by other servers (use GFS, fencing, blah, blah). I don't need the throughput of two live servers, I just want to be reasonably sure I have something that works even if one disk or one server dies and the only down-time is a couple of minutes for VRRP to kick in and for Windows users to re-map network drives.