RHEL: Handling SCSI disks

# Tested on RHEL 5, 6 & 7


# Check devices currently known to the SCSI subsystem
# ------------------------------------------------------------------------------------------

cat /proc/scsi/scsi
   Attached devices:
   Host: scsi0 Channel: 00 Id: 00 Lun: 00
     Vendor: VMware   Model: Virtual disk     Rev: 1.0
     Type:   Direct-Access                    ANSI SCSI revision: 02
   Host: scsi0 Channel: 00 Id: 01 Lun: 00
     Vendor: VMware   Model: Virtual disk     Rev: 1.0
     Type:   Direct-Access                    ANSI SCSI revision: 02


# NOTE: 'lsscsi' command can be used to display disks attached to server



# Identify a disk using 'scsi_id' command
# ------------------------------------------------------------------------------------------

# 'scsi_id' queries a SCSI device via the SCSI INQUIRY vital product data (VPD)
# page 0x80 or 0x83 and uses the resulting data to generate a value that is
# unique across all SCSI devices that properly support page 0x80 or page 0x83.

# It may be useful, for instance, to identify a disk shared by two nodes:

hostA:/#> scsi_id --page=0x83 --whitelisted --device=/dev/sdd
   36000c290d59b294f402f949a10afd541

hostB:/#> scsi_id --page=0x83 --whitelisted --device=/dev/sde
   36000c290d59b294f402f949a10afd541

# Depending on RHEL version, parameters and command location may vary slightly.
# More information about command usage:
# https://sites.google.com/site/syscookbook/rhel/rhel-scsi-identifier-show


# Add a SCSI disk to the system
# ------------------------------------------------------------------------------------------

# On this server we have: Host=0 (scsi0), Channel=0, Id=[0|1] and Lun=0  For a new disk
# we have to use, then, path 0.0.2.0 - SCSI(0:2).
# Once new disk has been attached/added to server, run following command to discover it:

echo "0 2 0" > /sys/class/scsi_host/host0/scan

# NOTE: We may know that host0 is the one to be used taking a look to the contents
#       of /proc/scsi/scsi file. In this case all disks are attached to scsi0 (host0)

# Alternatively we can run following commands in order to run a complete rescan:

for i in /sys/class/scsi_host/host*/scan; do echo "- - -" > $i; done



# Check

cat /proc/scsi/scsi
   Attached devices:
   Host: scsi0 Channel: 00 Id: 00 Lun: 00
     Vendor: VMware   Model: Virtual disk     Rev: 1.0
     Type:   Direct-Access                    ANSI SCSI revision: 02
   Host: scsi0 Channel: 00 Id: 01 Lun: 00
     Vendor: VMware   Model: Virtual disk     Rev: 1.0
     Type:   Direct-Access                    ANSI SCSI revision: 02
   Host: scsi0 Channel: 00 Id: 02 Lun: 00                              <--
     Vendor: VMware   Model: Virtual disk     Rev: 1.0
     Type:   Direct-Access                    ANSI SCSI revision: 02


lvmdiskscan
     /dev/ramdisk [       16.00 MB]
     /dev/root    [        8.00 GB]
     /dev/ram     [       16.00 MB]
     /dev/sda1    [      258.83 MB]
     /dev/dm-1    [       64.00 MB]
     /dev/ram2    [       16.00 MB]
     /dev/sda2    [      258.86 MB]
     /dev/dm-2    [        2.00 GB]
     /dev/ram3    [       16.00 MB]
     /dev/sda3    [       41.49 GB] LVM physical volume
     /dev/dm-3    [        2.00 GB]
     /dev/sdb     [       45.00 GB] LVM physical volume
   [...]
     /dev/sdc     [       20.00 GB]                      <--
     4 disks
     37 partitions
     1 LVM physical volume whole disk
     1 LVM physical volume


fdisk -l
[...]
   Disk /dev/sdc: 21.4 GB, 21474836480 bytes
   255 heads, 63 sectors/track, 2610 cylinders
   Units = cylinders of 16065 * 512 = 8225280 bytes

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



# Remove a SCSI disk from the system
# ------------------------------------------------------------------------------------------

# To remove a disk from server, once it has been removed from VG, etc, run following command:

echo 1 > /sys/block/<sdc>/device/delete


# Check

cat /proc/scsi/scsi
   Attached devices:
   Host: scsi0 Channel: 00 Id: 00 Lun: 00
     Vendor: VMware   Model: Virtual disk     Rev: 1.0
     Type:   Direct-Access                    ANSI SCSI revision: 02
   Host: scsi0 Channel: 00 Id: 01 Lun: 00
     Vendor: VMware   Model: Virtual disk     Rev: 1.0
     Type:   Direct-Access                    ANSI SCSI revision: 02
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