My Xen solution

This is the way I setup my servers running Xen. I'm working with IBM San DS4700 and IBM Bladecenter HS21.

+------+   +------+   +--------+     +--------+   +------+   +------+
| dom1 |   | dom2 |   | dom3   |     | dom4   |   | dom5 |   | dom6 |
|      |   |      |   |  ------|     |  ------|   |      |   |      |       [.... more domX ....]
|      |   |      |   |  |ocfs2|     |  |ocfs2|   |      |   |      |
+----|-+   +----|-+   +----|---+     +----|---+   +-|----+   +---|--+
  V  |       V  |       V  |           V  |        V|          V |
  |  |       |  |       |  |           |  |        ||          | |
  +==¦=======+==:=======+  |           +==:========+:==========+ |
  |  |          |          |           |  |         |            |
  |  +--------+++----------+           |  +--------+++-----------+
  |           |||                      |           |||
+-|-----------|||--------------+     +-|-----------|||--------------+
| OCFS2 | Xen HW |             |     | OCFS2 | Xen HW |             |
|-|-----------|||-             |     |-|-----------|||-             |       [.... more dom0 ....]
| |  dom0 (1) |||              |     | |  dom0 (2) |||              | 
+-|-----------|||--------------+     +-|-----------|||--------------+
  |           |||                      |   +-------¦+|
  +===========:::======================+   |       | |
  |           |||                          |       | |
  |           ||+==========================+===+===+ |
  |           |+---------------+      +----+   |     |
  |           +--------+       |      |        |     +--+
+-|--------------------|-------|------|--------|--------|-----------+
| SAN os_img_pool | Data1 | Data2 | Data3 | Data4   | Data5 |       |
|    (ocfs2)      | (xfs) | (xfs) | (xfs) | (ocfs2) | (xfs) |       |
|------------------------------------------------------------       |
| DS 4700 SAN                                                       |
+-------------------------------------------------------------------+

• All Xen images are on shared OCFS2 partitions. This allow easy live migration without network share.
• Data from databases are directly accessed on XFS partitions from domU.
• Data that need to be shared between domU are on OCFS2 partitions. For example there's a backup disk mount on each domU. A cronjob run on each domU and copy it's data on the backup disk, then a domU is responsible to send all those data to the TSM Library. So backup don't take much network workload and can be ran during the day (in fact there's always data flowing to the backup disk).
• Data flows between servers without using the network.

• When a dom0 fence, a whole bunch of domU disappear.
• Update need to be done carefully (OCFS2 protocol version change).
• It needs hardware that support it (a SAN).