SAS RAID 0 on Linux

We have a Dell PowerEdge R900 server with two SAS 300GB disk forming a RAID 1. There was a need of around 2TB of space and for that reason we bought 2 x 1TB SAS disks and attached them on the machine.
I’d expect that Linux (Scientific Linux 5.2) would automatically see the disks and display them on the “fdisk -l” output. But unfortunately that didn’t work. Checking with “dmesg” the disks were detected (and the PERC controller of course):

megasas: FW now in Ready state
scsi1 : LSI SAS based MegaRAID driver
  Vendor: SEAGATE   Model: ST3300555SS       Rev: T211
  Type:   Direct-Access                      ANSI SCSI revision: 05
  Vendor: SEAGATE   Model: ST3300555SS       Rev: T211
  Type:   Direct-Access                      ANSI SCSI revision: 05
  Vendor: SEAGATE   Model: ST31000640SS      Rev: MS04
  Type:   Direct-Access                      ANSI SCSI revision: 05
  Vendor: SEAGATE   Model: ST31000640SS      Rev: MS04
  Type:   Direct-Access                      ANSI SCSI revision: 05
usb 1-7: new high speed USB device using ehci_hcd and address 3
  Vendor: DP        Model: BACKPLANE         Rev: 1.06
  Type:   Enclosure                          ANSI SCSI revision: 05
  Vendor: DELL      Model: PERC 6/i          Rev: 1.11
  Type:   Direct-Access                      ANSI SCSI revision: 05

I was a bit puzzled on why the system didn’t show the disks while being detected. Checking under /proc/scsi/scsi just confirmed that the disks weren’t available to the system at all:

cat /proc/scsi/scsi 
Attached devices:
Host: scsi0 Channel: 00 Id: 32 Lun: 00
  Vendor: DP       Model: BACKPLANE        Rev: 1.06
  Type:   Enclosure                        ANSI SCSI revision: 05
Host: scsi0 Channel: 02 Id: 00 Lun: 00
  Vendor: DELL     Model: PERC 6/i         Rev: 1.11
  Type:   Direct-Access                    ANSI SCSI revision: 05

After a bit of Googling I came across a post on a forum which was saying that the disks should be built in a array in order to be available to the system. That actually means that the disks have to be Online and configured on the PERL controller and then the controller would make them available to the system. Next step was to reboot the machine and run the disk configuration utility.
While being in the utility, the steps for creating a RAID0 array for concatenating the disks’ were:
– Select the right PERC controller
– Check disks status on the Physical Disk Management page (the status indication for the new disks was “OFFLINE” so that explained to me why the disks weren’t accessible)
– Return to the Virtual Disk Management page
– Select Controller 1 from the top
– New Virtual Disk
– Select the two available hard drives
– Check available space
– Specify name
– Select stripe option
– OK
– Return to VD Management page
– Exit the utility
– Reboot the machine
– Job done 🙂

Then, “fdisk -l” would display the new /dev/sdb device with 2TB of space free. Just to confirm that everything was there:

cat /proc/scsi/scsi 
Attached devices:
Host: scsi1 Channel: 00 Id: 32 Lun: 00
  Vendor: DP       Model: BACKPLANE        Rev: 1.06
  Type:   Enclosure                        ANSI SCSI revision: 05
Host: scsi1 Channel: 02 Id: 00 Lun: 00
  Vendor: DELL     Model: PERC 6/i         Rev: 1.11
  Type:   Direct-Access                    ANSI SCSI revision: 05
Host: scsi1 Channel: 02 Id: 01 Lun: 00
  Vendor: DELL     Model: PERC 6/i         Rev: 1.11
  Type:   Direct-Access                    ANSI SCSI revision: 05

And the last thing was to create a huge filesystem and mount it on the system 🙂

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