[Linux-cluster] High availability xen cluster

[van Schelve]

Hello. I don't know if this here is the right list to discuss this but
maybe someone else with an equal scenario can describe how to best solve
this.

I plan to build a cluster environment with 6 or 8 nodes to provide xen
based virtual maschines. In our environment we have two data centre in
short rza and rzb. In addition we have a zoned SAN infra structure with a
Hitachi OPEN-V fabric in each data centre. My nodes are available to access
disks from both fabrics over multiple pathes. Please look at the following
multipath listing from one of my nodes: 

[root at ux072 ~]# multipath -l
mpath2_rzb (1HITACHI_R450F8D41022) dm-9 HITACHI,OPEN-V
[size=30G][features=1 queue_if_no_path][hwhandler=0]
\_ round-robin 0 [prio=0][active]
 \_ 1:0:0:2 sdd 8:48   [active][undef]
 \_ 1:0:1:2 sdg 8:96   [active][undef]
 \_ 2:0:0:2 sdp 8:240  [active][undef]
 \_ 2:0:1:2 sds 65:32  [active][undef]
mpath2_rza (1HITACHI_R450F94D1022) dm-12 HITACHI,OPEN-V
[size=30G][features=1 queue_if_no_path][hwhandler=0]
\_ round-robin 0 [prio=0][active]
 \_ 1:0:2:2 sdj 8:144  [active][undef]
 \_ 1:0:3:2 sdm 8:192  [active][undef]
 \_ 2:0:2:2 sdv 65:80  [active][undef]
 \_ 2:0:3:2 sdy 65:128 [active][undef]
mpath0_rzb (1HITACHI_R450F8D41020) dm-7 HITACHI,OPEN-V
[size=30G][features=1 queue_if_no_path][hwhandler=0]
\_ round-robin 0 [prio=0][active]
 \_ 1:0:0:0 sdb 8:16   [active][undef]
 \_ 1:0:1:0 sde 8:64   [active][undef]
 \_ 2:0:0:0 sdn 8:208  [active][undef]
 \_ 2:0:1:0 sdq 65:0   [active][undef]
mpath0_rza (1HITACHI_R450F94D1020) dm-10 HITACHI,OPEN-V
[size=30G][features=1 queue_if_no_path][hwhandler=0]
\_ round-robin 0 [prio=0][active]
 \_ 1:0:2:0 sdh 8:112  [active][undef]
 \_ 1:0:3:0 sdk 8:160  [active][undef]
 \_ 2:0:2:0 sdt 65:48  [active][undef]
 \_ 2:0:3:0 sdw 65:96  [active][undef]
mpath1_rzb (1HITACHI_R450F8D41021) dm-8 HITACHI,OPEN-V
[size=30G][features=1 queue_if_no_path][hwhandler=0]
\_ round-robin 0 [prio=0][active]
 \_ 1:0:0:1 sdc 8:32   [active][undef]
 \_ 1:0:1:1 sdf 8:80   [active][undef]
 \_ 2:0:0:1 sdo 8:224  [active][undef]
 \_ 2:0:1:1 sdr 65:16  [active][undef]
mpath1_rza (1HITACHI_R450F94D1021) dm-11 HITACHI,OPEN-V
[size=30G][features=1 queue_if_no_path][hwhandler=0]
\_ round-robin 0 [prio=0][active]
 \_ 1:0:2:1 sdi 8:128  [active][undef]
 \_ 1:0:3:1 sdl 8:176  [active][undef]
 \_ 2:0:2:1 sdu 65:64  [active][undef]
 \_ 2:0:3:1 sdx 65:112 [active][undef]

There are three disks in each data centre. Currently I only use the disks
in rza.

At the moment I'm testing with a two node cluster. The virtual machines are
on SAN disks and I can live migrate from one node to the other one. But
what I have to cover is the disaster. What happens when the fabric in rza
crashes? My virtual maschines are unavailable. What I'm thinking about is a
hardware based
mirroring between the both fabrics and break up the mirror when the
disaster happens or we need to power off the storage for maintenance. But
my problem is that I see duplicate pv id's in this situation. I cannot
mirror based on lvm because it is too slow.

Thank you for your ideas.

-- Hans-Gerd van Schelve