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seaweed
Asked: 2011-10-15 02:47:28 +0800 CST

mixing single path and multipath SR's in a Xenserver pool

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Has anyone attempted to run a single path iSCSI SR alongside a multipath iSCSI SR in a Xenserver 5.6 pool?

We're migrating from an old SAN to a new one and I want the new one to use multipathing.

Firstly, is this possible? If so, what steps will I need to follow and will I need to take the current SAN offline while enabling multipathing on the Xen hosts to get the new multipathed SR online? Are there any major pitfalls I should be aware of?

Any advice would be great.

iscsi storage xenserver

1 Answers

  1. My understanding is that this will work just fine. Consider two iSCSI LUNs. LUN A is presented with one path. LUN B is presented with multiple paths. Remember that the number of paths that a LUN is presented on, is a storage-side configuration item, not a server-side configuration.

    If MPIO is not enabled on the XenServer host, LUN B will be seen as multiple disks, even though it is actually one disk across multiple paths. If MPIO is enabled on the XenServer host, MPIO will recognize that these "multiple disks" are in fact multiple paths to the same LUN (LUN B) and use MPIO to manage I/O to LUN B. Meanwhile LUN A still has only one path and is treated as such.

    You should have no problems.

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