>>>>> "Doug" == Douglas Gilbert <dgilb...@interlog.com> writes:
>> So this takes me to a corner I still don't understand, if a LUN is >> pre-formatted as T10-protected, what happens to unwritten blocks >> read? I mean, SCSI login executes some reads from sevel LBAs which >> will probably fail as blocks are unwritten. Doug> Some observations: I haven't seen any disks pre-formatted with Doug> T10-protection, they usually come pre-formatted without Doug> T10-protection. Depends where you buy them. All the drives we ship arrive formatted with T10 PI from the manufacturer. However, nobody expects you to format a LUN on an array. When you create a LUN on a PI-capable storage array, T10 PI is a storage management interface option just like size, RAID level, etc. Upon creation, arrays zero out newly provisioned LUN blocks and write parity, etc. If PI is enabled on a LUN, blocks are written with all zeroes in the data block and all ones in the trailing PI tuple. This is all part of the regular LUN setup procedure. In any case. The usage model is that you never format a disk unless you are a tinkerer and bought a retail SAS drive at Fry's. Drives will be delivered by your server vendor formatted with PI and ready to go. If you use a non-disk storage device, whether or not to enable PI is part of the LUN provisioning procedure (array management console, RAID or flash controller card config utility, etc.) Doug> So a tentative READ, for example checking if a disk has a Doug> partition table, could be preceded by a GET LBA STATUS Doug> command. IMO, if provisioning is enabled, LBPRZ=0 then the GET LBA Doug> STATUS command should be mandatory. Otherwise a tentative READ is Doug> a lucky dip. It's perfectly valid to do a legacy/unprotected READ from a T10 PI device. Doesn't matter whether the blocks are unwritten or not. -- Martin K. Petersen Oracle Linux Engineering -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
