On Tue, 2007-10-30 at 00:19 -0500, Alberto Alonso wrote:

On Sat, 2007-10-27 at 12:33 +0200, Samuel Tardieu wrote:

quoted

I agree with Doug: nothing prevents you from using md above very slow
drivers (such as remote disks or even a filesystem implemented over a
tape device to make it extreme). Only the low-level drivers know when
it is appropriate to timeout or fail.

  Sam

The problem is when some of these drivers are just not smart
enough to keep themselves out of trouble. Unfortunately I've
been bitten by apparently too many of them.

Really, you've only been bitten by three so far.  Serverworks PATA
(which I tend to agree with the other person, I would probably chock
this up to Serverworks, not PATA), USB storage, and SATA (the SATA stack
is arranged similar to the SCSI stack with a core library that all the
drivers use, and then hardware dependent driver modules...I suspect that
since you got bit on three different hardware versions that you were in
fact hitting a core library bug, but that's just a suspicion and I could
well be wrong).  What you haven't tried is any of the SCSI/SAS/FC stuff,
and generally that's what I've always used and had good things to say
about.  I've only used SATA for my home systems or workstations, not any
production servers.

I'll repeat my plea one more time. Is there a published list
of tested combinations that respond well to hardware failures
and fully signals the md code so that nothing hangs?

I don't know of one, but like I said, I've not used a lot of the SATA
stuff for production.  I would make this one suggestion though, SATA is
still an evolving driver stack to a certain extent, and as such, keeping
with more current kernels than you have been using is likely to be a big
factor in whether or not these sorts of things happen.

If not, I would like to see what people that have experienced
hardware failures and survived them are using so that such
a list can be compiled.

-- 
Doug Ledford [off-list ref]
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              http://people.redhat.com/dledford

Infiniband specific RPMs available at
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