Dell forcing Linux customers to abandon software RAID?

James Ralston qralston+ml.dell-poweredge at andrew.cmu.edu
Fri Feb 23 12:38:12 CST 2007


On 2007-02-22 at 09:19-06 Patrick_Boyd at dell.com wrote:
> To answer your first question.  The simple answer is no.  If you use
> OMSA it will query the over all SMART status and display that as the
> "Failure Predicted" field in the disk information, but that's about
> it.

As an aside, this is one of the major reasons why we dislike using
hardware RAID on Linux systems.

If we use software RAID (via the Linux md driver), we can use the
smartmontools package (included by default in virtually all Linux
distros) to not only monitor drive health, but examine drive
statistics (temperature et. al.), schedule self-tests, etc.  In
contrast, hardware RAID controllers don't offer any additional
information/capabilities beyond "failure predicted" (if that).

In short, compared to the tools available by the OS, the hardware RAID
controller offers crippled SMART functionality.

We've been profoundly disappointed with what Dell has done with the
PowerEdge 2950 servers: not only does the PERC controller fail to
present the disks to the OS if it's disabled, but according to the
Dell engineer we spoke to yesterday, the only way to swap a SAS
(non-RAID) versus PERC (RAID) configuration for the 2950 is to replace
the system board.  Furthermore, if you want to purchase a SAS
(non-RAID) configuration, you are limited to the 4-disk backplane; you
cannot use the 6-disk or 8-disk backplane.

Also worrisome to us is that Dell's next-generation PowerVaults (the
MD3000 and MD1000) require hardware RAID; no JBOD mode is supported.

There are environments in which software RAID is better; there are
environments in which hardware RAID is better.  But Dell seems to have
embraced hardware RAID at the expense of treating customers who wish
to run software RAID instead as second-class citizens, and this
disturbs us, because in our experience, software RAID is frequently a
better solution for Linux systems than hardware RAID.



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