[CentOS] Megraid SAS virtual disc question

nate centos at linuxpowered.net
Fri Feb 1 21:47:27 UTC 2008


Joseph L. Casale wrote:
> Hi,
> Is there something OS related (CentOS 5.1) I would need to do for a CLI
> created array to become visible to the OS after the array is created and
> initialized? I don't want to reboot...


If your not currently using the array, you may be able to unload
the module and reload it.

If the devices from that array show up as SCSI devices you may be
able to interface with the /proc/scsi/scsi interface to add the new
volume

cat /proc/scsi/scsi

and use

echo "scsi add-single-device X X X X" >/proc/scsi/scsi
e.g.

/proc/scsi/scsi on one of my systems:
Attached devices:
Host: scsi0 Channel: 00 Id: 00 Lun: 24
  Vendor: 3PARdata Model: VV               Rev: 0000
  Type:   Direct-Access                    ANSI SCSI revision: 05
Host: scsi1 Channel: 00 Id: 00 Lun: 00
  Vendor: 3PARdata Model: VV               Rev: 0000
  Type:   Unknown                          ANSI SCSI revision: 05
Host: scsi1 Channel: 00 Id: 00 Lun: 24
  Vendor: 3PARdata Model: VV               Rev: 0000
  Type:   Direct-Access                    ANSI SCSI revision: 05
Host: scsi0 Channel: 00 Id: 00 Lun: 25
  Vendor: 3PARdata Model: VV               Rev: 0000
  Type:   Direct-Access                    ANSI SCSI revision: 05
Host: scsi1 Channel: 00 Id: 00 Lun: 25
  Vendor: 3PARdata Model: VV               Rev: 0000
  Type:   Direct-Access                    ANSI SCSI revision: 05


Assuming I only had 1 controller, scsi0, and I created a new
volume to export to the system, it's likely that volume would have
a different LUN. I would do:

echo "scsi add-single-device 0 0 0 1" >/proc/scsi/scsi

assuming the array used LUN 1 to export to the system. Then if
you cat /proc/scsi/scsi again the device will show up and will
be accessible. If nothing shows up then that device doesn't exist.

Not knowing how megaraid exports a virtual disk I'm not sure what
LUN it might assign, or maybe it presents it as a new ID number
instead of a new LUN.

nate




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