> -----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 ��.n��������+%������w��{.n�����{������ܨ}���Ơz�j:+v�����w����ޙ��&�)ߡ�a����z�ޗ���ݢj��w�f
