[CentOS] 3ware disk failure -> hang -- SCSI backplanes

Sat Jan 7 05:22:35 UTC 2006
Bryan J. Smith <thebs413 at earthlink.net>

Les Mikesell wrote:
> The only relevant part of the backplane is that
> it uses SCA connectors which you need for hot swapping
> because they make the power and data connections happen
> in the right order.  The controller doesn't know if
> there is a backplane or just a cable.

Chris Mauritz wrote:
> That is my understanding as well, though I'm not a bona fide certified 
> electrical engineer (don't even play one on the net).  8-)

Ummm, no, there's far more to a SCSI-2 backplane than just handling the
transient.  That is then feed back to the SCSI-2 host adapter.  And
depending on what the SCSI-2 driver can give the kernel, there's a lot
more that _can_ be reported.

And, my latter comment of ...

  "I'd have to fully research _what_ is exactly required -- at the SCSI
   card (probably not much), at the SCSI backplane (probably not much)
   and at the SCSI driver (there's the  majority of the beef ;-)."

SCSI-2 is a very rich command set, with a lot of control.  I'm sure the
backplane and host adapter offer a wealth of information, something that
can be used.  Again, I have to research what is different.

But _regardless_, you're _not_ going to get that out of a 3Ware, an
Areca, etc...  They have that capability _on_card_ in their firmware,
executed by their ASIC/microcontrollers for their arrays.  But they
aren't feeding back such a rich set of capabilities to the OS.

And that's before we even look at standard ATA controllers.  There is a
rich set of logic being developed for ATA, and "libata" attempts to
support it.  But nothing is well developed, much less well supported by
various controllers, etc...

So please quit nit-picking my comments, which you guys _always_ do.  I
have given far more dissection than _anyone_ here has even _bothered_ to
address.  I have given repeated, _sound_advise_ on what you can and
can't use 3Ware for.  There are far more many people going, "oh yeah,
you can use 3Ware and get hot-swap with software RAID" on a whim over on
the MD lists.  I at least know what I have used.

I'm honestly considering leaving this group because select people
continue to want to over-simplify my comments just for the sake of
disagreeing with them, and not seeing the larger issue of _all_ the
factors involved.  It's really not worth it if some of you guys don't
want to work with me.

And damn it if it isn't the same characters over and over and over
again.  Especially the ones that want me to provide documentation, yet
they haven't offered any insight or documentation themselves.

Bryan J. Smith   mailto:b.j.smith at ieee.org
Some things (or athletes) money can't buy.
For everything else there's "ManningCard."