Re: Tera-Byte+ fileservers

[Seth Mos <knuffie@xs4all.nl>]

On Fri, 24 Aug 2001, Bryan-TheBS-Smith wrote:

> Seth Mos wrote:
> > And use it in a SMP system or with a CPU watchdog enabled.
> > This triggers the watchdog which otherwise would not.
> 
> Yeah.  Do they work fine in SMP systems without a CPU watchdog? 

As far as I can tell from messages on the list, yes.

> I've only used them in single processor systems.

I have not seen any reports yet about the 3ware card in a UNI proccesor
with the software watchdog.


> P.S.  When you say "CPU watchdog" is that the kernel software
> watchdog, or a BIOS/CMOS setting?

The software watchdog. The more or less Bios versions (well it's mot
really a bios). The hardware watchdog works as follows.

You boot the machine and the kernel or a user application reads a address
that is documented in the docs that came with the motherboard. (or it
should). The first time you read this address the hardware watchdog is
switched on and will watch that address for further reads. If this this
does not happen within the timeout (that you specify in the bios) the
watchdog/Bios will send a reset signal.

I can think of the situation that during extremely heavy IO or CPU use the
kernel or software watchdog can not read the address before the timeout
and along comes your journaling fs to the rescue :-)
It may be that the timeout is to small for your occasion and you need to
make it higher. The motherboard I have starts at 10 secs and can go up to
a minute. Although this seems long it will be better then having your box
killed when it was in fact very busy.

IIRC the limit of the software watchdog is 5 (!) seconds which might be
the problem. It will also mean that you will have to wait longer before it
reboots.

Nice to see you around again.

Cheers