I've finally started to test the newer versions of RedHat 6.x and Scientific Linux on HP ProLiant hardware. My previous installs were in virtual hardware, so I didn't notice the raid controller driver change. The first thing I realized on a physical installation was that the drive array devices are now SCSI /dev/sdX names versus the longtime /dev/cciss/cXdX block devices.

Apparently, this is due to a new device driver, hpsa instead of cciss. Can anyone shed some light on the differences between the drivers?

What's gained? What's lost?
Is there any performance impact?
Is there any overlap in terms of the card supported?
Has there been a similar change on the Windows side?


HP has a good write-up of what the differences are here:

http://h20000.www2.hp.com/bc/docs/support/SupportManual/c02677069/c02677069.pdf (PDF)

High points:

  • Puts devices in the standard /dev namespace, which you already noticed.
  • Modernized interaction with the SCSI layer in newer kernels.
  • hpsa is a SCSI driver, cciss is a block-driver.
    • This will change device numbering, if that matters.
    • This is why the /dev namespace changes
  • The /sys controls for the driver will change.
  • Older cards (before the P400-era cards) still require CCISS
  • It may be the case that cciss and hpsa will both load if cards requiring them are present.

The Windows side is untouched.

  • This is perfect... Although, I may need to be versed in how to use Udev persistence to avoid a USB key or other SCSI drive from renumbering the controller device name. But I noticed RHEL 6 also embraced UUID's instead of LABELS for partitions as well... – ewwhite May 23 '11 at 16:15

http://cciss.sourceforge.net/#news is a good start. There is some overlap, with options to control behaviour of the drivers where there is overlap. I have not noticed any performance difference, but I have not done any proper testing.

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