[Scst-devel] Windows Server 2012 and reclaim feature

[Sergey T. <ser...@op...>]

Good afternoon.

We have found that Windows 2012 is not able to use reclaim feature with 
thin-provisioned disks that are served by SCST.

According to "SCSI Block Commands – 3" document:

"The device server in a logical unit that supports logical block 
provisioning management shall set:
a) the LBPME bit to one in the parameter data returned for a READ 
CAPACITY (16) command
(see 5.16.2); and
b) the PROVISIONING TYPE field to 000b in the Logical Block Provisioning 
VPD page (see 6.5.4).
The initial condition of every LBA in a thin provisioned logical unit is 
deallocated."

But it looks like SCST trims VPD 0xB2 page size to 2, instead of correct 
size 4 value. Trimed bytes contain PROVISIONING TYPE field wich we guess 
sufficient for correct provisioning detection by Windows 2012 platform.

We have prepared an easy patch against latest SCST trunk (r4977), which 
tries to fix VPD 0xB2 page size. We have tested it in our environment 
and it seems to work. Could you please consider the patch as a solution 
for the problem?

Thank you.
Sergey.