topic Re: Windows MPIO question in StoreVirtual Storage

Windows MPIO question

eschneid — Fri, 03 Jun 2011 15:19:35 GMT

We keep getting different stories on how the DSM/MPIO for Windows works. 1 person says we should see traffic down all storage NICs, 1 says it is just to have connections to extra nodes to quicken failover, 1 says we should be getting reads/writes from all the nodes at the same time, etc.

I just need a real world explanation of how the software is supposed to work.

SAN/iQ 9.0
Windows 2008 R2

Thanks

Re: Windows MPIO question

Jitun — Fri, 03 Jun 2011 17:20:12 GMT

You have the following options for setting up MPIO with the SAN/iQ software:
Using the HP StorageWorks P4000 DSM, which provides the following
â ¢ Lower latency because of the direct path to each data page in a volume.
â ¢ Better write performance.
â ¢ Load always evenly distributed.
â ¢ Recommended for clusters with three or more storage systems where select servers need the
lower latency and additional throughput afforded by a session to every storage system.

Using the Microsoft DSM, which provides the following:
â ¢ Comes with Microsoft MPIO.
â ¢ Uses fewer iSCSI connections.
â ¢ Supports mixed access to SAN/iQ volumes from both Windows servers and VMWare ESX
servers.
â ¢ Provides the basic needs of MPIO, I/O path high availability, and load balancing for most servers, without installing a custom driver.

The HP P4000 DSM for MPIO enables fault-tolerant paths to the SAN storage systems while increasing available bandwidth to the SAN for superior performance. When a Windows server running iSCSI connects to a volume on the SAN, it establishes an active iSCSI session to each storage system in the cluster.
The P4000 DSM for MPIO enables an application server to continually communicate with the storage system that is hosting a copy of the data that the server is requesting. The SAN/iQ software aggregates the Ethernet connections, processing power, and storage capacity of all systems. This aggregation
increases performance and capacity as you add storage systems to the network.

The P4000 DSM for MPIO provides enhanced MPIO functionality as follows:
â ¢ Automatic creation of an I/O path to each storage system in the cluster on which the volume resides, plus a path for the administrative connection.
â ¢ Improved performance architecture over native MPIO solutions:
â ¢ Read I/Os are always serviced by a storage system that holds a copy of the data being re-quested.
â ¢ Write I/Os are always serviced by a storage system that receives a copy of the data. Remaining copies (replicas) of the data are forwarded to the appropriate storage system based on the data protection level of the volume.
â ¢ The ability to build a robust, fault-tolerant solution because an I/O path is built to every storage
system in the cluster.
For example, in a cluster with five storage systems, DSM for MPIO-connected volumes have six iSCSI MPIO connections to the SAN, one for each storage system and one for the administrative connection. Five of the six connections could go offline, and I/O would still be
serviced.

Re: Windows MPIO question

Thomas Halwax — Mon, 06 Jun 2011 13:35:55 GMT

@Jitun,

thanks for your detailed answer. I have two questions:

1) What is the recommendation for running Windows Server 2003 MPIO as a guest in an VMWare 4.1 cluster? (no MPIO, MS or HP). I need VSS support so raw device mapping is not an issue.

2) What do you mean when you say "Supports mixed access to SAN/iQ volumes from both Windows servers and VMWare ESX
servers."

Thanks in advance,
Thomas

Re: Windows MPIO question

Jitun — Thu, 09 Jun 2011 01:57:27 GMT

Regarding the 1st question
If the VM is connecting up to the LUN directly, rather than using a portion of what is presented to the hypervisor, and that VM has multiple paths to the LUN, a multi-pathing solution is required. So a win2k guest OS directly connecting to a LUN would need to run MPIO.

Regarding the 2nd question
Actually it beats me too :)

Re: Windows MPIO question

Uwe Zessin — Thu, 09 Jun 2011 05:03:30 GMT

2) "Supports mixed access to SAN/iQ volumes from both Windows servers and VMWare ESX servers."

I think that is when you use VMware Consolidated Backup (VCB).
You can't / must not use the P4000 DSM in that combination.

Re: Windows MPIO question

Thomas Halwax — Mon, 13 Jun 2011 19:03:34 GMT

@Jitun and Uwe,

thanks for your answers!

Thomas