I created an md device on two fibre channel disks, sde and sdf. I then disabled the switch port to which the hba is connected. After the remote port time out messages, I re-enabled the switch port. Three things happen that are weird. First, two unexpected responses while scanning. Second, the creation of sdm and sdn. Third, the md device remains inaccessible. I don't think this is working the way it's intended to. I suspect it will cause big problems for multi-path volume managers in a fail back situation. Mike duck /root# ls /sys/block hda loop1 loop4 loop7 ram10 ram13 ram2 ram5 ram8 sdb sde sdh sdk hdc loop2 loop5 ram0 ram11 ram14 ram3 ram6 ram9 sdc sdf sdi sdl loop0 loop3 loop6 ram1 ram12 ram15 ram4 ram7 sda sdd sdg sdj duck /root# mdadm --create /dev/md0 --level stripe -n 2 /dev/sde /dev/sdf md: bind<sde> md: bind<sdf> md0: setting max_sectors to 128, segment boundary to 32767 raid0: looking at sdf raid0: comparing sdf(35843584) with sdf(35843584) raid0: END raid0: ==> UNIQUE raid0: 1 zones raid0: looking at sde raid0: comparing sde(35843584) with sdf(35843584) raid0: EQUAL raid0: FINAL 1 zones raid0: done. raid0 : md_size is 71687168 blocks. raid0 : conf->hash_spacing is 71687168 blocks. raid0 : nb_zone is 1. raid0 : Allocating 8 bytes for hash. mdadm: array /dev/md0 started. duck /root# cat /proc/mdstat Personalities : [linear] [raid0] [raid1] [raid5] [raid4] [multipath] md0 : active raid0 sdf[1] sde[0] 71687168 blocks 64k chunks unused devices: <none> duck /root# dd if=/dev/md0 bs=256k count=1 of=/dev/null 1+0 records in 1+0 records out 262144 bytes (262 kB) copied, 0.0133771 seconds, 19.6 MB/s ************************* portdisable 11 on fibre channel switch ******************* duck /root# rport-5:0-0: blocked FC remote port time out: removing target and saving binding rport-5:0-1: blocked FC remote port time out: removing target and saving binding rport-5:0-2: blocked FC remote port time out: removing target and saving binding rport-5:0-3: blocked FC remote port time out: removing target and saving binding rport-5:0-4: blocked FC remote port time out: removing target and saving binding rport-5:0-5: blocked FC remote port time out: removing target and saving binding rport-5:0-6: blocked FC remote port time out: removing target and saving binding rport-5:0-7: blocked FC remote port time out: removing target and saving binding rport-5:0-8: blocked FC remote port time out: removing target and saving binding rport-5:0-9: blocked FC remote port time out: removing target and saving binding rport-5:0-10: blocked FC remote port time out: removing target and saving binding rport-5:0-11: blocked FC remote port time out: removing target and saving binding rport-5:0-12: blocked FC remote port time out: removing target and saving binding rport-5:0-13: blocked FC remote port time out: removing target and saving binding rport-5:0-14: blocked FC remote port time out: removing target and saving binding rport-5:0-15: blocked FC remote port time out: removing target and saving binding duck /root# ls /sys/block hda loop1 loop4 loop7 ram1 ram12 ram15 ram4 ram7 sda sdd hdc loop2 loop5 md0 ram10 ram13 ram2 ram5 ram8 sdb loop0 loop3 loop6 ram0 ram11 ram14 ram3 ram6 ram9 sdc duck /root# !dd dd if=/dev/md0 bs=256k count=1 of=/dev/null 5:0:8:0: rejecting I/O to dead device Buffer I/O error on device md0, logical block 0 Buffer I/O error on device md0, logical block 1 Buffer I/O error on device md0, logical block 2 Buffer I/O error on device md0, logical block 3 Buffer I/O error on device md0, logical block 8 Buffer I/O error on device md0, logical block 9 Buffer I/O error on device md0, logical block 10 Buffer I/O error on device md0, logical block 11 Buffer I/O error on device md0, logical block 16 Buffer I/O error on device md0, logical block 17 5:0:9:0: rejecting I/O to dead device 5:0:8:0: rejecting I/O to dead device dd: reading `/dev/md0': Input/output error 0+0 records in 0+0 records out 0 bytes (0 B) copied, 0.0655691 seconds, 0.0 kB/s ************************* portenable 11 on fibre channel switch ******************* Vendor: SGI Model: Universal Xport Rev: 0615 Type: Direct-Access ANSI SCSI revision: 03 5:0:0:31: Attached scsi generic sg4 type 0 Vendor: SGI Model: Universal Xport Rev: 0615 Type: Direct-Access ANSI SCSI revision: 03 5:0:1:31: Attached scsi generic sg5 type 0 Vendor: SGI Model: Universal Xport Rev: 0615 Type: Direct-Access ANSI SCSI revision: 03 5:0:2:31: Attached scsi generic sg6 type 0 Vendor: SGI Model: Universal Xport Rev: 0615 Type: Direct-Access ANSI SCSI revision: 03 5:0:3:31: Attached scsi generic sg7 type 0 Vendor: SGI Model: Universal Xport Rev: 0615 Type: Direct-Access ANSI SCSI revision: 03 5:0:4:31: Attached scsi generic sg8 type 0 Vendor: SGI Model: Universal Xport Rev: 0615 Type: Direct-Access ANSI SCSI revision: 03 5:0:5:31: Attached scsi generic sg9 type 0 Vendor: SGI Model: Universal Xport Rev: 0615 Type: Direct-Access ANSI SCSI revision: 03 5:0:6:31: Attached scsi generic sg10 type 0 Vendor: SGI Model: Universal Xport Rev: 0615 Type: Direct-Access ANSI SCSI revision: 03 5:0:7:31: Attached scsi generic sg11 type 0 Vendor: SGI Model: ST336753FC Rev: 2701 Type: Direct-Access ANSI SCSI revision: 03 SCSI device sdg: 71687372 512-byte hdwr sectors (36704 MB) sdg: Write Protect is off sdg: Mode Sense: ab 00 10 08 SCSI device sdg: drive cache: write back w/ FUA SCSI device sdg: 71687372 512-byte hdwr sectors (36704 MB) sdg: Write Protect is off sdg: Mode Sense: ab 00 10 08 SCSI device sdg: drive cache: write back w/ FUA sdg: sdg1 sdg9 sdg11 sd 5:0:8:0: Attached scsi disk sdg sd 5:0:8:0: Attached scsi generic sg12 type 0 Vendor: SGI Model: ST336753FC Rev: 2701 Type: Direct-Access ANSI SCSI revision: 03 error 1 5:0:8:0: Unexpected response from lun 0 while scanning, scan aborted <<<<<<<<<<<<<<<<<<<<<<< Vendor: SGI Model: ST336753FC Rev: 2701 Type: Direct-Access ANSI SCSI revision: 03 SCSI device sdh: 71687372 512-byte hdwr sectors (36704 MB) sdh: Write Protect is off sdh: Mode Sense: ab 00 10 08 SCSI device sdh: drive cache: write back w/ FUA SCSI device sdh: 71687372 512-byte hdwr sectors (36704 MB) sdh: Write Protect is off sdh: Mode Sense: ab 00 10 08 SCSI device sdh: drive cache: write back w/ FUA sdh: sdh1 sdh9 sdh11 sd 5:0:9:0: Attached scsi disk sdh sd 5:0:9:0: Attached scsi generic sg13 type 0 Vendor: SGI Model: ST336753FC Rev: 2701 Type: Direct-Access ANSI SCSI revision: 03 error 1 5:0:9:0: Unexpected response from lun 0 while scanning, scan aborted <<<<<<<<<<<<<<<<<<<<<<<<<< Vendor: SGI Model: ST336753FC Rev: 2701 Type: Direct-Access ANSI SCSI revision: 03 SCSI device sdi: 71687372 512-byte hdwr sectors (36704 MB) sdi: Write Protect is off sdi: Mode Sense: ab 00 10 08 SCSI device sdi: drive cache: write back w/ FUA SCSI device sdi: 71687372 512-byte hdwr sectors (36704 MB) sdi: Write Protect is off sdi: Mode Sense: ab 00 10 08 SCSI device sdi: drive cache: write back w/ FUA sdi: sdi1 sdi9 sdi11 sd 5:0:10:0: Attached scsi disk sdi sd 5:0:10:0: Attached scsi generic sg14 type 0 Vendor: SGI Model: ST336753FC Rev: 2701 Type: Direct-Access ANSI SCSI revision: 03 SCSI device sdj: 71687372 512-byte hdwr sectors (36704 MB) sdj: Write Protect is off sdj: Mode Sense: ab 00 10 08 SCSI device sdj: drive cache: write back w/ FUA SCSI device sdj: 71687372 512-byte hdwr sectors (36704 MB) sdj: Write Protect is off sdj: Mode Sense: ab 00 10 08 SCSI device sdj: drive cache: write back w/ FUA sdj: sdj1 sdj9 sdj11 sd 5:0:11:0: Attached scsi disk sdj sd 5:0:11:0: Attached scsi generic sg15 type 0 Vendor: SGI Model: ST336753FC Rev: 2701 Type: Direct-Access ANSI SCSI revision: 03 SCSI device sdk: 71687372 512-byte hdwr sectors (36704 MB) sdk: Write Protect is off sdk: Mode Sense: ab 00 10 08 SCSI device sdk: drive cache: write back w/ FUA SCSI device sdk: 71687372 512-byte hdwr sectors (36704 MB) sdk: Write Protect is off sdk: Mode Sense: ab 00 10 08 SCSI device sdk: drive cache: write back w/ FUA sdk: sdk1 sdk9 sdk11 sd 5:0:12:0: Attached scsi disk sdk sd 5:0:12:0: Attached scsi generic sg16 type 0 Vendor: SGI Model: ST336753FC Rev: 2701 Type: Direct-Access ANSI SCSI revision: 03 SCSI device sdl: 71687372 512-byte hdwr sectors (36704 MB) sdl: Write Protect is off sdl: Mode Sense: ab 00 10 08 SCSI device sdl: drive cache: write back w/ FUA SCSI device sdl: 71687372 512-byte hdwr sectors (36704 MB) sdl: Write Protect is off sdl: Mode Sense: ab 00 10 08 SCSI device sdl: drive cache: write back w/ FUA sdl: sdl1 sdl9 sdl11 sd 5:0:13:0: Attached scsi disk sdl sd 5:0:13:0: Attached scsi generic sg17 type 0 Vendor: SGI Model: ST336753FC Rev: 2701 Type: Direct-Access ANSI SCSI revision: 03 SCSI device sdm: 71687372 512-byte hdwr sectors (36704 MB) sdm: Write Protect is off sdm: Mode Sense: ab 00 10 08 SCSI device sdm: drive cache: write back w/ FUA SCSI device sdm: 71687372 512-byte hdwr sectors (36704 MB) sdm: Write Protect is off sdm: Mode Sense: ab 00 10 08 SCSI device sdm: drive cache: write back w/ FUA sdm: sdm1 sdm9 sdm11 sd 5:0:14:0: Attached scsi disk sdm sd 5:0:14:0: Attached scsi generic sg18 type 0 Vendor: SGI Model: ST336753FC Rev: 2701 Type: Direct-Access ANSI SCSI revision: 03 SCSI device sdn: 71687372 512-byte hdwr sectors (36704 MB) sdn: Write Protect is off sdn: Mode Sense: ab 00 10 08 SCSI device sdn: drive cache: write back w/ FUA SCSI device sdn: 71687372 512-byte hdwr sectors (36704 MB) sdn: Write Protect is off sdn: Mode Sense: ab 00 10 08 SCSI device sdn: drive cache: write back w/ FUA sdn: sdn1 sdn9 sdn11 sd 5:0:15:0: Attached scsi disk sdn sd 5:0:15:0: Attached scsi generic sg19 type 0 duck /root# ls /sys/block hda loop1 loop4 loop7 ram1 ram12 ram15 ram4 ram7 sda sdd sdi sdl hdc loop2 loop5 md0 ram10 ram13 ram2 ram5 ram8 sdb sdg sdj sdm loop0 loop3 loop6 ram0 ram11 ram14 ram3 ram6 ram9 sdc sdh sdk sdn duck /root# cat /proc/mdstat Personalities : [linear] [raid0] [raid1] [raid5] [raid4] [multipath] md0 : active raid0 sdf[1] sde[0] 71687168 blocks 64k chunks unused devices: <none> duck /root# !dd dd if=/dev/md0 bs=256k count=1 of=/dev/null 5:0:8:0: rejecting I/O to dead device printk: 23 messages suppressed. Buffer I/O error on device md0, logical block 0 Buffer I/O error on device md0, logical block 1 Buffer I/O error on device md0, logical block 2 Buffer I/O error on device md0, logical block 3 Buffer I/O error on device md0, logical block 8 Buffer I/O error on device md0, logical block 9 Buffer I/O error on device md0, logical block 10 Buffer I/O error on device md0, logical block 11 Buffer I/O error on device md0, logical block 16 Buffer I/O error on device md0, logical block 17 5:0:9:0: rejecting I/O to dead device 5:0:8:0: rejecting I/O to dead device dd: reading `/dev/md0': Input/output error 0+0 records in 0+0 records out 0 bytes (0 B) copied, 0.154544 seconds, 0.0 kB/s - : 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