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I have been spending quite a bit of time digging through old SCSI and controller specs. As far as I can tell the original Linux behavior was correct. Recent SPC specs are very abstract in this department resulting in unfortunate ambiguity. But originally PQ=1 meant "LUN supports this peripheral device type but no physical device is currently connected". Based on this original definition, PQ=1 has been widely used throughout the industry as a means to avoid associating an ULD driver with a device. The LUN is accessible (primary commands, etc.) but no media is present (no physical device connected). Our original algorithm, which I would like to reinstate, is essentially the following (in slightly unrolled form): if (PQ == 3) /* Don't expose device */ else if ((PQ == 1 || sdev->pdt_1f_for_no_lun) && PDT == 0x1f) /* Don't expose device */ else if (PQ == 1) { /* Expose device, don't bind ULD */ } else /* PQ == 0 */ /* Expose device, bind ULD if PDT is supported */ I would like to understand why -- in the case of the IBM 2145 -- exposing the sg device caused problems. Li: Can you shed some light on the problems caused by 2145 LUNs reporting PQ=1? Thanks! -- Martin K. Petersen Oracle Linux Engineering