Thursday, 6 October 2011

Rescan dynamically the scsi bus (applicable to CX Clariion SAN infrastructure)

Rescan dynamically the scsi bus

I've been working for a while with a Dell - Clariion CX-300, and the best way to add new attached LUNs was always to reboot the server.
However, that procedure is not always the most acceptable if you're in a hurry or if just want to do some tests.
I found the procedure described above, in an outdated website, but worked very well in my case.

I also recommend to use rescan-scsi-bus.sh script with the options -lwc. Type rescan-scsi-bus.sh --help to see the description of each option.

/root/rescan-scsi-bus.sh
Host adapter 1 (qla2xxx) found.
Host adapter 2 (qla2xxx) found.
Scanning for device 1 0 0 0 ...
OLD: Host: scsi1 Channel: 00 Id: 00 Lun: 00
Vendor: DGC Model: LUNZ Rev: 0208
Type: Direct-Access ANSI SCSI revision: 04
Scanning for device 2 0 0 0 ...
OLD: Host: scsi2 Channel: 00 Id: 00 Lun: 00
Vendor: DGC Model: LUNZ Rev: 0208
Type: Direct-Access ANSI SCSI revision: 04
0 new device(s) found.
0 device(s) removed.



So I stoped powerpath and unload qla modules in order to restart the whole thing.
$ /etc/init.d/PowerPath stop
Stopping PowerPath: done
$ lsmod | grep qla
qla6312 119233 0
qla2xxx 165733 1 qla6312
scsi_transport_fc 12225 1 qla2xxx
scsi_mod 116941 5 sg,qla2xxx,scsi_transport_fc,megaraid_mbox,sd_mod
[root@pasargades /opt/Navisphere/bin]
$ modprobe -r qla6312 qla2xxx
[root@pasargades /opt/Navisphere/bin]
$ lsmod | grep qla



then reload the whole thing:

$ modprobe qla2xxx qla6312
[root@pasargades /opt/Navisphere/bin]
$ /etc/init.d/PowerPath start
Starting PowerPath: done



then it works, the kernel does see the new devices

$ cat /proc/scsi/scsi
Attached devices:
Host: scsi0 Channel: 00 Id: 06 Lun: 00
Vendor: PE/PV Model: 1x2 SCSI BP Rev: 1.0
Type: Processor ANSI SCSI revision: 02
Host: scsi0 Channel: 01 Id: 00 Lun: 00
Vendor: MegaRAID Model: LD 0 RAID1 69G Rev: 521S
Type: Direct-Access ANSI SCSI revision: 02
Host: scsi3 Channel: 00 Id: 00 Lun: 00
Vendor: DGC Model: RAID 5 Rev: 0208
Type: Direct-Access ANSI SCSI revision: 04
Host: scsi3 Channel: 00 Id: 00 Lun: 01
Vendor: DGC Model: RAID 5 Rev: 0208
Type: Direct-Access ANSI SCSI revision: 04
Host: scsi4 Channel: 00 Id: 00 Lun: 00
Vendor: DGC Model: RAID 5 Rev: 0208
Type: Direct-Access ANSI SCSI revision: 04
Host: scsi4 Channel: 00 Id: 00 Lun: 01
Vendor: DGC Model: RAID 5 Rev: 0208
Type: Direct-Access ANSI SCSI revision: 04
[root@pasargades /opt/Navisphere/bin]
$ fdisk -l

Disk /dev/sda: 73.2 GB, 73274490880 bytes
255 heads, 63 sectors/track, 8908 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System
/dev/sda1 1 4 32098+ de Dell Utility
/dev/sda2 * 5 583 4650817+ 83 Linux
/dev/sda3 584 1220 5116702+ 83 Linux
/dev/sda4 1221 8908 61753860 5 Extended
/dev/sda5 1221 3770 20482843+ 83 Linux
/dev/sda6 3771 5682 15358108+ 83 Linux
/dev/sda7 5683 6192 4096543+ 82 Linux swap

Disk /dev/sdb: 676.4 GB, 676457349120 bytes
255 heads, 63 sectors/track, 82241 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Disk /dev/sdb doesn't contain a valid partition table

Disk /dev/sdc: 1395.8 GB, 1395864371200 bytes
255 heads, 63 sectors/track, 169704 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Disk /dev/sdc doesn't contain a valid partition table

Disk /dev/sdd: 676.4 GB, 676457349120 bytes
255 heads, 63 sectors/track, 82241 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Disk /dev/sdd doesn't contain a valid partition table

Disk /dev/sde: 1395.8 GB, 1395864371200 bytes
255 heads, 63 sectors/track, 169704 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Disk /dev/sde doesn't contain a valid partition table

Disk /dev/emcpowera: 676.4 GB, 676457349120 bytes
255 heads, 63 sectors/track, 82241 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Disk /dev/emcpowera doesn't contain a valid partition table

Disk /dev/emcpowerb: 1395.8 GB, 1395864371200 bytes
255 heads, 63 sectors/track, 169704 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Disk /dev/emcpowerb doesn't contain a valid partition table




REmarque: We can see that fdisk sees double path 'raw' devices ( /dev/sdb and /dev/sdd ) to a same device, which finnaly is presented by powerpath as /dev/emcpowera . All disk system command (fdisk etc ...) should now use that device in order to benefit the use of powerpath (load balancing and failover on our double attached FC ).//

The 'rescan' script shows that now:

$ /root/rescan-scsi-bus.sh
Host adapter 3 (qla2xxx) found.
Host adapter 4 (qla2xxx) found.
Scanning for device 3 0 0 0 ...
OLD: Host: scsi3 Channel: 00 Id: 00 Lun: 00
Vendor: DGC Model: RAID 5 Rev: 0208
Type: Direct-Access ANSI SCSI revision: 04
Scanning for device 4 0 0 0 ...
OLD: Host: scsi4 Channel: 00 Id: 00 Lun: 00
Vendor: DGC Model: RAID 5 Rev: 0208
Type: Direct-Access ANSI SCSI revision: 04
0 new device(s) found.
0 device(s) removed.

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