Peter Grandi wrote:
> If you have high availability requirements perhaps you should buy
> from an established storage vendor a storage system designed by
> integration engineers and guaranteed by the vendor for some high
> availability level.
Actually, I don't trust such systems. That's our main reason for using
software RAID 1: if all else fails with regard to RAID, we can take one
of the disks and mount it as a non-RAID ext3 file system. No
"guaranteed" proprietary system can offer that.
(And other than this one perplexing problem, we've been extremely happy
with software RAID for many years -- thanks, Neal and everyone else
involved.)
> Perhaps without realizing it you have engaged in storage system
> design and integration and there are many, many, many, many subtle
> pitfalls in that (as the archives of this list show abundantly).
>
> You cannot just slap things together and it all works. Have you
> done even sketchy common mode failure analysis?
Ouch! :-)
Just for the record, this isn't "slapped together" hardware. They're
off-the-shelf, server-grade, currently sold, genuine Intel, etc.
SuperMicro servers, with no modifications, specifically chosen because
they're widely used. The only storage system design we've done is
connect a SATA drive to each of the two motherboard SATA ports and use
software RAID 1 (yeah, I know that's "design", and we did think about it
and test it, but still).
We've done many stress/failure tests for data storage, all of which pass
as expected. What I unfortunately can't test in advance is how they
behave when a working hard disk suddenly has a mechanical failure, which
is the only time we've seen a problem.
I could sacrifice a working disk by opening it up while running and
poking the platters with a screwdriver (I've seriously considered this),
but repeating the test more than a few times would get expensive.
> Also putting two drives belonging to a RAID set on the same
> IDE/ATA channel is usually a bad idea for performance too.
They're SATA drives. There's no actual IDE hardware involved.
--
Robert L Mathews
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