MPIO FF DSM, Persistent Binding and WinSrv2003 Disk Numbers

[Neil Lowden]

Hi

Is there anyway to ensure that vdisks presented by an EVA8100 to Windows Server 2003 retain a consistemt disk number across reboots?

Basically I want to ensure the same vdisk is always at the same disk number in Windows Disk Management.

I have explored persistent binding in SANsurfer but that appears to operate below the MPIO layer and Iassume that is not what I need.

Thanks

-Neil

[IBaltay]

Hi,
this could help you:
http://h20000.www2.hp.com/bc/docs/support/SupportManual/c01535361/c01535361.pdf?jumpid=reg_R1002_USEN

[IBaltay]

and this:
http://data.versiontracker.com/drivers/autoExtract/hp/ftp2/pub/softpaq/sp40001-40500/sp40386_ext/extract/readme.txt

[Neil Lowden]

Thanks for those documents, unfortunately the second refers to Emulex HBA's whereas I am using QLogic.

For testing, I have 3 vdisks on the EVA8100 presented to Windows. HP MPIO DSM Manager correctly shows 3 LUNs with 8 available paths each. In the LUN display, the LUNs each have a Disk Number and B-T-L but whenever I right-click and refresh, the B-T-L's change. If this is normal then it suggests it's not possible to lock a vdisk to a specific Windows Disk Number.

-Neil

[IBaltay]

Hi,
one thing is the loadbalancing in which the MPIO ALB is checking e.g. the less utilized path (from EVA8100 8 paths) and starts the HBA IO on it. This is dynamical according e.g. to the IO queues, etc.

the other thing is to keep nicely the numbering identical between the EVA and the host. This means, that the best is giving unique numbers of the vdisks on the EVA side to the host side and thus the LUN numbers will be identical on both EVA and host side. (besides the VDISK WWN unique identifier).
This is not changing and it is stable during the reboots, because it comes from the EVA itself and the OS is getting it during the boot when the HBAs are scanning the EVA LUNs

[Urban Petry]

This can only be ensured if the number of presented vdisks and their (EVA) LUN assignment _and_ the number of local disks doesn't change!

For each EVA VDisk the MPIO driver creates windows devices like "\Device\MPIODisk0" (counting up for further Vdisks), which show up in Disk Management in order of their numbering. Since they're created in order of their (EVA) LUN assignment, the VDisk presented to LUN 1 will always become MPIODisk0. But if a formerly existent VDisk ist (temporarily) missing, the next VDisk will inherit the device name of the former VDisk on next reboot.

And don't forget the local disks (e.g. adding or removing a local drive on a SmartArray controller) can change your overall Windows disk numbering depending on where the SmartArray controller is "placed".

Urban