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Windows MPIO DSM - How Many Sessions?

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Paul Hutchings
Super Advisor

Windows MPIO DSM - How Many Sessions?

I've installed the P4000 Windows DSM MPIO on a 2008 R2 box with 2 iSCSI NICs.

I've then created and assigned luns in the CMC.

In the MS iSCSI initiator I've followed the guide in the Windows Solution Pack, so:

Added the vip's and done a refresh
Connected each volume twice - once for each iSCSI NIC/IP
Changed MPIO from "vendor specific" to "Round Robin"

And I'm seeing that in the CMC if I look at each volume I don't see the same number of sessions for each one.

LUN1 shows 6 connections to node1 (3 from each NIC)
LUN2 shows 2 connections to node2 (1 from each NIC)
LUN3 shows 6 connections to node3 (3 from each NIC)
LUN4 shows 4 connections to node4 (2 from each NIC)
LUN5 shows 2 connections to node1 (1 from each NIC)

Does this seem/sound normal please?

Thanks in advance,
Jay Cardin
Frequent Advisor

Re: Windows MPIO DSM - How Many Sessions?

That doesn't seem right and according to this document ( it isn't right.

Does the eventlog from msiscsi that show any MPIO errors?

You might want to delete the target portals, reboot and enter them in again.
Paul Hutchings
Super Advisor

Re: Windows MPIO DSM - How Many Sessions?

Thanks Jay. I uninstalled/reinstalled stripped out everything and it didn't seem to make a huge difference.

Then I moved my server to the same site as some of my storage, rebooted it, and now I have DSM sessions showing up?!

See, we have two sites with P4000 nodes in them running in network raid 10, but the cluster uses a single subnet and is a stretch LAN, so in theory a server can connect to any node in any site, so I didn't assign the server to a site because when I do that it "prefers" the servers in that site, if that makes sense?

I'm logging it with HP as I think I may have found a quirk or "something" that isn't clearly documented, or it may just be co-incidence.

Trusted Contributor

Re: Windows MPIO DSM - How Many Sessions?


This is by Design.
Its called Site Aware feature.
Hence the Server on the Site connects only to the Storage Systems on the same Site.
Hence the performance is much better.

Server Aware Sites

HP StorageWorks SAN/iQ software version 9.0 sites can be defined to contain specific host servers which enhances the load balancing and path management capabilities of the SAN for all MPIO and load balancing modes. Some of these enhancements were available previous to 9.0 but required multiple subnets to be used in the multi-site SAN. All load balancing improvements can now be used in either single subnet, or multi-subnet clusters.

When servers and storage nodes are assigned to sites using the HP P4000 CMC:

HP P4000 DSM sessions are automatically connected to only the storage systems that are in the same site as the host sever. This reduces overall session count and improves performance by favoring IO connections to storage systems that are more local to the host.

All other (non HP P4000 DSM) sessions are automatically load balanced to storage systems in the same site if the volume is not already being accessed at another site.
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Paul Hutchings
Super Advisor

Re: Windows MPIO DSM - How Many Sessions?

Thanks Jitun (and thanks for the support assuming you're the same chap).

For everyone else, as Jitun says it is the site aware feature, *but* it appears that if you aren't organized and simply leave your servers in "Unassigned" it uses DSM and connects to nodes in all sites.

I tried being tidy and created a site called "Servers" and put a server in it - when you do this it doesn't appear to use DSM, only regular MPIO.

I've asked for clarification from L2 and a possible feature request as it seems a little contrary to benefit from being disorganized :)

T Buis
Occasional Advisor

Re: Windows MPIO DSM - How Many Sessions?

Your link no longer resolves!   Any idea of the name of the manual that you referenced?