How to get physical partition name from iSCSI details on Windows?

Posted by Barry Kelly on Server Fault See other posts from Server Fault or by Barry Kelly
Published on 2012-06-29T03:44:49Z Indexed on 2012/06/30 9:17 UTC
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I've got a piece of software that needs the name of a partition in \Device\Harddisk2\Partition1 style, as shown e.g. in WinObj. I want to get this partition name from details of the iSCSI connection that underlies the partition. The trouble is that disk order is not fixed - depending on what devices are connected and initialized in what order, it can move around.

So suppose I have the portal name (DNS of the iSCSI target), target IQN, etc. I'd like to somehow discover which volumes in the system relate to it, in an automated fashion.

I can write some PowerShell WMI queries that get somewhat close to the desired info:

PS> get-wmiobject -class Win32_DiskPartition
NumberOfBlocks   : 204800
BootPartition    : True
Name             : Disk #0, Partition #0
PrimaryPartition : True
Size             : 104857600
Index            : 0
...

From the Name here, I think I can fabricate the corresponding name by adding 1 to the partition number: \Device\Harddisk0\Partition1 - Partition0 appears to be a fake partition mapping to the whole disk.

But the above doesn't have enough information to map to the underlying physical device, unless I take a guess based on exact size matching.

I can get some info on SCSI devices, but it's not helpful in joining things up (iSCSI target is Nexenta/Solaris COMSTAR):

PS> get-wmiobject -class Win32_SCSIControllerDevice
__GENUS             : 2
__CLASS             : Win32_SCSIControllerDevice
...
Antecedent          : \\COBRA\root\cimv2:Win32_SCSIController.DeviceID="ROOT\\ISCSIPRT\\0000"
Dependent           : \\COBRA\root\cimv2:Win32_PnPEntity.DeviceID="SCSI\\DISK&VEN_NEXENTA&PROD_COMSTAR...

Similarly, I can run queries like these:

PS> get-wmiobject -namespace ROOT\WMI -class MSiSCSIInitiator_TargetClass
PS> get-wmiobject -namespace ROOT\WMI -class MSiSCSIInitiator_PersistentDevices

These guys return information relating to my iSCSI target name and the GUID volume name respectively (a volume name like \\?\Volume{guid-goes-here}), but the GUID volume name is no good to me, and there doesn't appear to be a reliable correspondence between the target name and the volume that I can join on.

I simply can't find an easy way of getting from an IQN (e.g. iqn.1992-01.com.example:storage:diskarrays-sn-a8675309) to physical partitions mapped from that target.

The way I do it by hand? I start Disk Management, and look for a partition of the correct size, verify that its driver says NEXENTA COMSTAR, and look at the disk number. But even this is unreliable if I have multiple iSCSI volumes of the exact same size.

Any suggestions?

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