Problem with random disks mount sequence

[Lamar Owen]

On Wednesday 12 December 2007, Les Mikesell wrote:
> I'm starting to build a box that will have an assortment of scsi and
> sata disks, most, but not all paired in md raid1 devices and expect to
> have a few hotplug sata and external USB and firewire drives that will
> be connected periodically.  Do you have any hints on how to write a
> script that will copy things to the recently-mounted drive(s) and how to
> avoid boot problems if any of them happen to be connected during a
> reboot?  Will the md devices always find/pair themselves regardless of
> the underlying partition device names?

MD devices will find their mates by UUID.  Drive order matters not to MD.  Let 
me show you an example from a large Linux machine I have here:

[root at spacely ~]# cat /proc/mdstat
Personalities : [raid1] [raid5]
md1 : active raid5 sdq1[3] sdh1[4] sdg1[2] sdc1[1] sdb1[0]
      71765760 blocks level 5, 64k chunk, algorithm 2 [5/5] [UUUUU]

md2 : active raid5 sdu1[5](S) sds1[6](S) sdp1[7](S) sdo1[4] sdk1[3] sdi1[2] 
sdf1[1] sde1[0]
      142249728 blocks level 5, 64k chunk, algorithm 2 [5/5] [UUUUU]

md0 : active raid1 sdn1[2](S) sdm1[1] sdl1[0]
      8843200 blocks [2/2] [UU]

unused devices: <none>
[root at spacely ~]#   

The only place where drive order matters is where /boot lives, and that's set, 
for PC hardware, in the GRUB configuration.

Oh, in case your wondering what sort of hardware this is, here's the contents 
of /proc/scsi/scsi: the clues you need to find out what kind of system this 
is are in there. :-)
[root at spacely ~]# cat /proc/scsi/scsi
Attached devices:
Host: scsi0 Channel: 00 Id: 00 Lun: 00
  Vendor: SEAGATE  Model: ST318436LC       Rev: 0004
  Type:   Direct-Access                    ANSI SCSI revision: 03
Host: scsi0 Channel: 00 Id: 01 Lun: 00
  Vendor: SEAGATE  Model: ST318436LC       Rev: 0004
  Type:   Direct-Access                    ANSI SCSI revision: 03
Host: scsi0 Channel: 00 Id: 02 Lun: 00
  Vendor: SEAGATE  Model: ST318436LC       Rev: 0004
  Type:   Direct-Access                    ANSI SCSI revision: 03
Host: scsi0 Channel: 00 Id: 03 Lun: 00
  Vendor: SEAGATE  Model: ST39103LCSUN9.0G Rev: 034A
  Type:   Direct-Access                    ANSI SCSI revision: 02
Host: scsi0 Channel: 00 Id: 04 Lun: 00
  Vendor: SEAGATE  Model: ST336607LC       Rev: DS09
  Type:   Direct-Access                    ANSI SCSI revision: 03
Host: scsi0 Channel: 00 Id: 05 Lun: 00
  Vendor: SEAGATE  Model: ST336607LC       Rev: DS09
  Type:   Direct-Access                    ANSI SCSI revision: 03
Host: scsi0 Channel: 00 Id: 14 Lun: 00
  Vendor: SYMBIOS  Model: D1000            Rev: 2
  Type:   Processor                        ANSI SCSI revision: 02
Host: scsi1 Channel: 00 Id: 08 Lun: 00
  Vendor: SEAGATE  Model: ST318436LC       Rev: 0004
  Type:   Direct-Access                    ANSI SCSI revision: 03
Host: scsi1 Channel: 00 Id: 09 Lun: 00
  Vendor: SEAGATE  Model: ST318436LC       Rev: 0004
  Type:   Direct-Access                    ANSI SCSI revision: 03
Host: scsi1 Channel: 00 Id: 10 Lun: 00
  Vendor: SEAGATE  Model: ST336607LC       Rev: 0007
  Type:   Direct-Access                    ANSI SCSI revision: 03
Host: scsi1 Channel: 00 Id: 12 Lun: 00
  Vendor: SEAGATE  Model: ST39103LCSUN9.0G Rev: 034A
  Type:   Direct-Access                    ANSI SCSI revision: 02
Host: scsi1 Channel: 00 Id: 13 Lun: 00
  Vendor: SEAGATE  Model: ST336607LC       Rev: DS09
  Type:   Direct-Access                    ANSI SCSI revision: 03
Host: scsi1 Channel: 00 Id: 15 Lun: 00
  Vendor: SYMBIOS  Model: D1000            Rev: 2
  Type:   Processor                        ANSI SCSI revision: 02
Host: scsi2 Channel: 00 Id: 01 Lun: 00
  Vendor: SEAGATE  Model: ST39103LCSUN9.0G Rev: 034A
  Type:   Direct-Access                    ANSI SCSI revision: 02
Host: scsi2 Channel: 00 Id: 02 Lun: 00
  Vendor: SEAGATE  Model: ST39103LCSUN9.0G Rev: 034A
  Type:   Direct-Access                    ANSI SCSI revision: 02
Host: scsi2 Channel: 00 Id: 03 Lun: 00
  Vendor: SEAGATE  Model: ST39103LCSUN9.0G Rev: 034A
  Type:   Direct-Access                    ANSI SCSI revision: 02
Host: scsi2 Channel: 00 Id: 04 Lun: 00
  Vendor: COMPAQ   Model: BD036659CC       Rev: 3B00
  Type:   Direct-Access                    ANSI SCSI revision: 03
Host: scsi2 Channel: 00 Id: 05 Lun: 00
  Vendor: SEAGATE  Model: ST336605LSUN36G  Rev: 0238
  Type:   Direct-Access                    ANSI SCSI revision: 03
Host: scsi2 Channel: 00 Id: 08 Lun: 00
  Vendor: SEAGATE  Model: ST318436LC       Rev: 0004
  Type:   Direct-Access                    ANSI SCSI revision: 03
Host: scsi2 Channel: 00 Id: 09 Lun: 00
  Vendor: FUJITSU  Model: MAJ3182M SUN18G  Rev: 0804
  Type:   Direct-Access                    ANSI SCSI revision: 02
Host: scsi2 Channel: 00 Id: 10 Lun: 00
  Vendor: SEAGATE  Model: ST336605LSUN36G  Rev: 0238
  Type:   Direct-Access                    ANSI SCSI revision: 03
Host: scsi2 Channel: 00 Id: 11 Lun: 00
  Vendor: SEAGATE  Model: ST318436LC       Rev: 0004
  Type:   Direct-Access                    ANSI SCSI revision: 03
Host: scsi2 Channel: 00 Id: 13 Lun: 00
  Vendor: SEAGATE  Model: ST336607LC       Rev: DS09
  Type:   Direct-Access                    ANSI SCSI revision: 03
Host: scsi2 Channel: 00 Id: 14 Lun: 00
  Vendor: SYMBIOS  Model: D1000            Rev: 2
  Type:   Processor                        ANSI SCSI revision: 02
Host: scsi2 Channel: 00 Id: 15 Lun: 00
  Vendor: SYMBIOS  Model: D1000            Rev: 2
  Type:   Processor                        ANSI SCSI revision: 02
Host: scsi3 Channel: 00 Id: 05 Lun: 00
  Vendor: HP       Model: C1537A           Rev: L706
  Type:   Sequential-Access                ANSI SCSI revision: 02
Host: scsi3 Channel: 00 Id: 06 Lun: 00
  Vendor: TOSHIBA  Model: XM6201TASUN32XCD Rev: 1103
  Type:   CD-ROM                           ANSI SCSI revision: 02
[root at spacely ~]#   

I have had more problems with drive order on PC hardware than I have had on 
spacely.
-- 
Lamar Owen
Chief Information Officer
Pisgah Astronomical Research Institute
1 PARI Drive
Rosman, NC  28772
(828)862-5554
www.pari.edu