[8154] in linux-scsi channel archive
Re: recovery behaviour with 1 bad + 1 good drive (aic7xxx)
daemon@ATHENA.MIT.EDU (Ricky Beam)
Tue Feb 22 15:08:15 2000
Date: Tue, 22 Feb 2000 14:17:55 -0500 (EST)
From: Ricky Beam <jfbeam@bluetopia.net>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Matthias Andree <ma@dt.e-technik.uni-dortmund.de>,
linux-scsi@vger.rutgers.edu
In-Reply-To: <E12NJke-0002HT-00@the-village.bc.nu>
Message-ID: <Pine.LNX.4.04.10002221404330.12259-100000@beaker>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
On Tue, 22 Feb 2000, Alan Cox wrote:
>> Why, some RAID controllers are cheaper than Adaptec SCSI cards :-)
>
>A raid controller wont help you on a bus hang. I learned that the hard way
>last night when a MegaRAID got a bus hang and totalled my /usr/src in the
>process as I had it set to write back.
First rule, never set a RAID card to write-back. (esp. if you don't have
a BBU attached to it.) Don't acknowledge writes until they are actually
on the physical disk(s). I've had the same problem with a DPT controller
in a news server -- people would power it down or hit the reset button before
it was done flushing 128M of write behind data. HOWEVER, the news server
was not designed for reliablity; it was designed for speed.
(I know, I'm a fanatic.)
This depends on the firmware of the controller.
In my case, it would appear something as simple as a SCSI bus parity error
can crash a Mylex RAID controller. I don't know why the hell they won't
listen to me when I tell them it's crashing -- I even sent them the i960's
console data from boot to crash. (I sent the board for repair. Two months
later, I get it back with a new RTC battery on it !?!? That, of course,
didn't fix a damned thing -- it crashed 17 min. after I put it back in the
system. Needless to say, this REALLY pisses me off.)
(Note to the reader, the "Mylex Only" connector on the AccelRAID cards is
actually a serial port connected to the i960. 19200-8-n-1.)
>Ext2fs isnt happy when the last 20Mb of so of writes,(not in the order it wanted
>them to happen either) go missing.
Indeed. Add to that the effects of dcache and you have a recipe for
mke2fs :-)
--Ricky
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