Error Message

01/01/2015         11:27:40 PM       WARNING                 44(0x8007002c)           mpio                servername.domain         
One or more of your multipath adapters do not support extended SRBs.  You may experience suboptimal performance with device \Device\MPIODiskXX.

With Windows Server 2012 Microsoft has introduced a new structure in the storage I/O stack. STORAGE_REQUEST_BLOCK (extended SRB) is designed to replace the SCSI_REQUEST_BLOCK (legacy SRB). Extended SRBs replicate the functionality of the legacy SRBs, but are also extensible and scalable.

To benefit from extended SRB, all components in the storage stack must support this new structure. If any component in the stack does not yet support it, the above Warnings will be logged by MPIO.

Even though the Warning speaks about "suboptimal performance", currently extended SRBs do not offer any performance advantage over legacy SRB as these structures are not yet use by any application.

Storage Foundation is designed to offer the best possible performance for your mission-critical applications. Therefore we are testing this new structure and will add it into the next major release if any performance advantage can be gained by using it.

After installing Storage Foundation 6.1 or 6.0.2 with the DMP DSM feature, you might find Event ID 44 messages from MPIO in your event log:

01/01/2015         11:27:40 PM       WARNING                 44(0x8007002c)           mpio                servername.domain         
One or more of your multipath adapters do not support extended SRBs.  You may experience suboptimal performance with device \Device\MPIODiskXX.

The note about suboptimal performance might raise some concerns. This article explains the reasons for these Warnings