On 11-12-05 03:33 AM, Sampathkumar, Kishore wrote:
In SCSI-3 SPC, I was going through the section on "Device Identification VPD Page" (Section 7.6.3). I see the following: If "Association" field in VPD83 page is set to 00b (i.e., The IDENTIFIER field is associated with the addressed logical unit), the above standard says: At least one identification descriptor should have the IDENTIFIER TYPE field set to: a) 2h (i.e., EUI-64-based); b) 3h (i.e., NAA); or c) 8h (i.e., SCSI name string). Going through the details of (a) and (b), I notice that they are numeric. However, (c) above is an ASCII string. But, even in this case, if the first 4 UTF-8 characters are parsed, the rest of it contains numeric value in ASCII. For all SCSI disks that are SCSI-3 SPC compliant, for the above case, is it safe to say: each of them shall have an associated "numeric value" that is "unique" (assuming that the 4 UTF-8 characters for "SCSI name string" format are stored/available).
"Logical Unit name" is the most recent t10.org term to describe the "designator" (no longer called "identifier") whose association is 00b in the Device Identification VPD page (83h). SCSI transport standards say very little about Logical Unit (LU) names. For example SPL-2 (SAS) says the LU name should be different from the target port identifiers and target device name of the device (disk) that contains the LU. In other words there are 3 NAA-5 values that the LU name of a SAS disk can _not_ be. You have found what SPC-3 (and SPC-4) says about LU names. That is it, nothing else. In SPC-4 the definition of a SCSI name string for a lead-in of ".iqn" (as used by iSCSI) breaks your assertion: "If the ASSOCIATION field is set to 00b (i.e., logical unit) and the SCSI NAME STRING field starts with the four UTF-8 characters 'iqn.', the SCSI NAME STRING field ends with the five UTF-8 characters ',L,0x' concatenated with 16 hexadecimal digits for the logical unit name extension. The logical unit name extension is a UTF-8 string containing no more than 16 hexadecimal digits. The logical unit name extension is assigned by the SCSI target device vendor and shall be assigned so the logical unit name is worldwide unique." Unlikely but possible is that a SAS fabric has a SAS to iSCSI bridge located behind a SAS target so any LUs behind that bridge are in a iSCSI domain. Such iSCSI LUs would most likely follow iSCSI LU naming conventions. So a SAS application client running on Linux could see a LU name like this: "iqn.2001-04.com.example,L,0x0000000000000000" Doug Gilbert -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
