X3T9.2/88-012 January 19, 1988 TO: John Lohmeyer, X3T9.2 Committee (SCSI) Chairman From: John Farnsworth Datapoint Corporation Subject: Request for Clarification of FORMAT UNIT command In the SCSI I specification for the FORMAT UNIT command (Section 8.1.2), the statement is made: "The FORMAT UNIT command ensures that the medium is formatted so that all data blocks can be accessed". The same statement is then echoed in CCS4B and SCSI II. From our experience with multiple suppliers of SCSI disk products, if the FOV bit is set and the DCRT (disable certification) bit is set (do not certify), the FORMAT UNIT command will complete in one pass across the disk surface. It is our intention to format the disk as quickly as possible and then follow up with an initiator controlled surface verification. We have identified a drive which takes the specification literally and forces an ID field verification pass after the format pass, even with the FOV and DCRT bits set. If the ID verification pass fails, then the FORMAT UNIT command is aborted with CHECK CONDITION status. The only way to recover from this error, since you can't determine if it failed in the format pass or the verify pass, is to add the block address given when REQUEST SENSE is issued, to the defect list and reissue the FORMAT UNIT command. This means that the format which was expected to take about 10 minutes may take hours. With other drives, we are able to make an initiator controlled surface verification and then handle all the additional errors at once by REASSIGN BLOCKS or by reissuing the FORMAT UNIT command with an updated defect list. I propose that an editorial clarification be made to the SCSI II rev 3 working draft, section 8.1.1 FORMAT UNIT command, first sentence below table 8-2: FROM The FORMAT UNIT command (Table 8-2) ensures that the medium is formatted so that all of the initiator addressable logical blocks may be accessed. TO The FORMAT UNIT command (Table 8-2) formats the medium into initiator addressable logical blocks, subject to initiator defined options. and at the point where the DCRT bit is defined: FROM A DCRT bit of one indicates that the target shall not perform the target-specific medium certification process while formatting. TO A DCRT bit of one indicates that the target shall not perform any target-specific medium certification process or format verification process while executing the FORMAT UNIT command. An editorial clarification is proposed because I believe that the intent of SCSI is to allow the initiator to override the target's default parameters when the initiator also takes the responsibility for its action. Thank you for your consideration, John D. Farnsworth