A few things, mostly technical notes...

Monday, September 26, 2005

devlabel shows different page80 identifiers on multipathed devices

I've 5 multipathed luns from Symmetrix as shown below, (Lun 0 being vol. logix database)


Attached scsi disk sda at scsi0, channel 0, id 0, lun 0
Attached scsi disk sdb at scsi0, channel 0, id 0, lun 2
Attached scsi disk sdc at scsi0, channel 0, id 0, lun 3
Attached scsi disk sdd at scsi0, channel 0, id 0, lun 4
Attached scsi disk sde at scsi0, channel 0, id 0, lun 5
Attached scsi disk sdf at scsi1, channel 0, id 0, lun 0
Attached scsi disk sdg at scsi1, channel 0, id 0, lun 2
Attached scsi disk sdh at scsi1, channel 0, id 0, lun 3
Attached scsi disk sdi at scsi1, channel 0, id 0, lun 4
Attached scsi disk sdj at scsi1, channel 0, id 0, lun 5

Let us examine lun 2. The device names are /dev/sdb and /dev/sdg.

/dev/sdb (primary path)

# devlabel printid -d /dev/sdb
S80:373031303731303231303330EMCSYMMETRIX

/dev/sdg (alt path)

# devlabel printid -d /dev/sdg
S80:373031303731303231333031EMCSYMMETRIX

The SCSI Page 80 identifiers of /dev/sdb and /dev/sdg should be identical, both being dual paths to the same device. BUT THEY ARE DIFFERENT...(!!??)


Lets use scsi_unique_id to examine /dev/sdb and /dev/sdg further:

/dev/sdb

# scsi_unique_id /dev/sdb
model: EMC SYMMETRIX
page80: 373031303731303231303330
page83 type6: 00018570107153594d3032310000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000

/dev/sdg

# scsi_unique_id /dev/sdg
model: EMC SYMMETRIX
page80: 373031303731303231333031
page83 type6: 00018570107153594d3032310000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000


scsi_unique_id shows two different page80 identifiers: 373031303731303231303330 (sdb) and
373031303731303231333031 (sdg)..!!


(Oh yes, /dev/sdb and /dev/sdg are *indeed* alternate devices..!!)


System Details:

ES release 3 (Taroon Update 5) , 2.4.21-27.ELsmp, devlabel: 0.48.03


Update (10.27.05): They had to turn on C-Bit, and once they did that, this problem went away.

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