On Thu, 2013-11-21 at 17:37 +0000, Elliott, Robert (Server Storage) wrote: > > > -----Original Message----- > > From: Ewan Milne [mailto:emilne@xxxxxxxxxx] > > Sent: Monday, 18 November, 2013 11:29 AM > > To: Elliott, Robert (Server Storage) > > Cc: Ramesh Chikkanayakanahally; linux-scsi@xxxxxxxxxxxxxxx; > > jbottomley@xxxxxxxxxxxxx > > Subject: RE: Question on SCSI target scan > > > > On Fri, 2013-11-15 at 23:53 +0000, Elliott, Robert (Server Storage) > > wrote: > > > Beware that just because the LUN inventory is the same doesn't mean > > > the logical units are the same. A logical unit at LUN X might have been > > > deleted and another logical unit created and assigned to LUN X, but > > > now containing different content. You need to check the logical unit > > > name (in the Device Identification VPD page) too. > > > --- > > > Rob Elliott HP Server Storage > > > > > > > If the properties of the volume behind a particular LUN are changed, > > shouldn't something like ASC/ASCQ 3F 03 INQUIRY DATA HAS CHANGED, > > 3F 04 DEVICE IDENTIFIER CHANGED be reported? Or can we not expect > > this if a LUN is removed and then re-added without an intervening > > REPORT LUNS command? (In that case, the REPORT LUNS data returned > > will be no different.) > > > > -Ewan > > > > It might report that, and/or these: > VOLUME SET CREATED OR MODIFIED (3Fh/0Ah) > NOT READY TO READY CHANGE, MEDIUM MAY HAVE CHANGED (28h/00h) > > However, the device server in the new logical unit might not know that > there was a previous logical unit assigned to that LUN and might not know > all the INQUIRY data, mode page values, log page values, etc. values that > were in use to compare them to the current values, so is probably unable > to report the specifics of what changed. It will probably just report an > additional sense code with ASC=29h like POWER ON OCCURRED (29h/01h). > > Per the unit attention condition precedence level rules (see SAM-5 > revision 15 table 53), the additional sense codes with ASC=29h imply that > all other unit attention conditions might also have happened (INQUIRY > data changed, mode pages changed, log pages changed, capacity > changed, etc.). Software is supposed to assume the worst and check > everything again. I'm not confident that much software really does that, > though. > > The unit attention condition precedence is: > 1. POWER ON, RESET, OR BUS DEVICE RESET OCCURRED (29h/00h) > 2. POWER ON OCCURRED (29h/01h) or > DEVICE INTERNAL RESET (29h/04h) > 3. SCSI BUS RESET OCCURRED (29h/02h) or > MICROCODE HAS BEEN CHANGED (3Fh/01h) or > protocol specific (e.g., TRANSCEIVER MODE CHANGED > TO LVD 29h/06h in parallel SCSI) > 4. BUS DEVICE RESET FUNCTION OCCURRED (29h/03h) > 5. I_T NEXUS LOSS OCCURRED (29h/07h) > 6. COMMANDS CLEARED BY POWER LOSS NOTIFICATION (2Fh/01h) > 7. All others > > Also, for each ASC value, ASCQ=00h has precedence over all ASCQ values > that are nonzero. For example, PARAMETERS CHANGED (2Ah/00h) implies > that all the other 2Ah/xxh codes might have happened. > > --- > Rob Elliott HP Server Storage Useful information, thanks for the reply. -Ewan -- 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
