In Enterprise environment Linux operating systems were installed on various X86 ( HP / SUN ) models of hardware, and most of the times we dont use software Raid to mirror the Operating system harddisks, and we rely on the hardware RAID.

Below tips will be useful to identify the whether the linux OS are under hardware RAID or not. If OS disks are under control of HARDWARE RAID, then what type of Hardware RAID it is using.

Locating the Root Mount  and device information for “/”

 Issue the following command to identify the root volume name:

 # /bin/mount | grep “on / “

 This will produce similar to the following output:

 /dev/sda2 on / type ext3 (rw)

 The output above informs us that the root volume / is mounted on a device designated /dev/sda2.

 Syntax breakdown is as follows:

 s = SCSI

 d = disk

 a = first device

 2 = second partition

Older revisions of Linux used legacy disk attachment drivers that did not emulate SCSI and therefore reported themselves as follows:

 h = hard

 d = disk

 a = first device

 2 = second partition

We use the keyword SCSI because all storage devices in a modern Linux platform including IDE/PATA, FC-AL, SAS, SATA, SCSI, and USB emulate SCSI to be represented as a storage device.  

 Issue the following command to identify the attached disk properties:

 # /bin/more /proc/scsi/scsi

 This will produce similar to the following output depending on platform type and configuration:

 Scenario 1 Output :

Attached devices: 

Host: scsi0 Channel: 00 Id: 00 Lun: 00

Vendor: SEAGATE  Model: ST373207LC       Rev: 0003

Type:   Direct-Access                    ANSI SCSI revision: 03

Host: scsi0 Channel: 00 Id: 01 Lun: 00

Vendor: SEAGATE  Model: ST373207LC       Rev: 0003

Type:   Direct-Access                    ANSI SCSI revision: 03

Scenrio 2 Output:

Attached devices:

Host: scsi0 Channel: 00 Id: 00 Lun: 00

Vendor: LSILOGIC Model: 1030 IM       IM Rev: 1000

Type:   Direct-Access                    ANSI SCSI revision: 02

Scenario 3 Output:

Attached devices:

Host: scsi1 Channel: 02 Id: 00 Lun: 00

Vendor: MegaRAID Model: LD 0 RAID5  278G Rev: 413Y

Type:   Direct-Access                    ANSI SCSI revision: 02

So what did you see difference from the above three outputs.  We have to look at the two important parameters from the above output those are “Vendor” and “Disk Model”.

Scenario 1  – Analysis: 

This output identifies two SCSI disks attached to the internal controller. The internal controller is not shown in this output.
Note that both disks are shown in the Vendor: field as the true manufacturer disk name SEAGATE and the field Model: shows the true manufacturer disk model ST373207LC. 

This actually indicates that  these were not configured with any RAID because the Linux was able to access the disk model information directly.

Result: OS DISKS NOT UNDER THE CONTROL OF HARDWARE RAID MANAGEMENT

Scenario 2 – Analysis:

This output identifies one SCSI disk attached to the internal controller.

Note that the disk reported in the field Vendor: is LSILOGIC and the field Model: shows 1030 IM.

Here we see that the true disk manufacturer is hidden from the operating system and replaced with a pseudo volume name LSILOGIC. And the true disk model is replaced with an identifier providing us with the RAID controller name and configuration 1030 IM.

The 1030 refers to the LSI 1020/1030 controller built in to this platform. The IM refers to the configuration of RAID:

IS = Stripe / RAID 0

IM = Mirror / RAID 1

Result:OS DISKS UNDER THE CONTROL OF ONBOARD LSI HARDWARE RAID MANAGEMENT

Scenario 3 – Analysis:

This output identifies one SCSI disk attached to the internal controller. More devices may show if you have an intelligent disk backplane installed or additional disks not under hardware RAID control.

Note that the disk reported in the field Vendor: is MEGARAID and the field Model: shows LD 0 RAID5.

Here we see that the true disk manufacturer is hidden from the operating system and replaced with a pseudo volume name MEGARAID. The true disk model is replaced with an identifier providing us with the RAID controller ID and configuration LD 0 RAID5

Result : OS DISKS WERE UNDER THE CONTROL OF LSI MEGARAID HARDWARE RAID MANAGEMENT