Software RAID issues (was Re: Suggestions solicited, server bring up)

[Alan Johnson]

On Mon, Nov 16, 2009 at 10:39 AM, Chip Marshall <chip at 2bithacker.net> wrote:

>  No, I meant the hardware RAID. While yes, the drive array
> appears as a block device, that block device is being handled by
> a driver for the RAID controller, which can have flaws leading
> to problems.
>
> I don't recall the specific issue with the PERC under older 2.6
> Linux kernels, but I do recall having drive lockups under high
> drive utilization with FreeBSD 6.1-R, which was fixed in 6.2.
> That was with the PERC5/i in the 2850. I think the 2950 uses
> the PERC6.
>

Wow, that is interesting.  The only reason I've ever had to install a driver
for a RAID controller is for online management.  As far as drive access, all
the controllers I've come across just look like any other SATA or SCSI
controller from a device exposure.  The controller hides the real drives
from the system (not just the OS, but the entire system) and exposes the
RAID volumes as if they were drives.

Do these controllers work differently or do you thing there is just some
error in the implemtation of SATA or SCSI on the controllers or the Linux
drivers?  Or perhaps there is something surprisingly wrong with online
management driver?
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