Marginal disks prevent boot with mps(4)

[Dustin Wenz]

I just installed a build of 9.0-STABLE in order to test the changes since release. I was hoping that some of the error-handling in mps would alter the behavior I've seen with some SATA disks (particularly, Seagate ST3000DM001 disks) connected through an LSI SAS 9201-16e HBA.

It is apparently possible for these disks to get in a state where their presence prevents the machine from booting. This problem has existed for some time, according to some archive-searching I've done, but there isn't much consensus on how to fix it.

The disks are good enough that they can be probed at startup, but some part of initialization cannot complete. This is the message I see repeated forever upon boot (the probe number does change slightly):

	(probe14:mps0:0:14:0): INQUIRY. CDB: 12 0 0 0 24 0 length 36 SMID 215 terminated ioc 804b scsi 0 state c xfer 0

There is a comment in mps_sas.c which suggests that this error is usually transient, but that seems not to be the case here. Can anyone suggest a modification that might permit booting in this state?

	- .Dustin