Re: 2.4.17 RAID-1 EXT3 reliable to hang....

[Matti Aarnio]

On Fri, Jan 04, 2002 at 04:36:35PM +0200, Matti Aarnio wrote:
> For past few weeks I have wondered of why my web-server machine
> is hanging semi-regularly.

  Over the weekend I tried something new.
 
> I have:
>   - Two 30+ GB SCSI Ultra2-Wide disks
>   - onboard AIC7XXX controller
>   - Disks with identical partition maps
>   - RAID-1 bound pairwise on those partitions
>     (RAIDTAB entries md3/md4/md5 - the md0/md1/md2 were on
>      other older disk, which was removed latter..)
>   - EXT3 filesystem at all partitions (except at 2 G swap..)
>     Mounted with default options
>   - machine with dual-P-III 750 MHz, and 786 MB memory (3*256MB)

  .. running 2.4.17 code compiled with "SMP" disabled, but
  having APICs enabled. (e.g. Local and IO-APIC.)
  It appears to me as:
   - SMP code, SMP mode: hangup in use
   - SMP code, "nosmp" boot option: hangup in use
   - UP code: works

  Tool chain:

$ gcc -v
gcc version 2.96 20000731 (Red Hat Linux 7.1 2.96-97.1)
$ ld -V
GNU ld version 2.11.92.0.12 20011121

  I have partial evidence that EXT3 may be part of the problem,
  as another machine with RAID-1 disks with EXT2 filesystems
  is not hanging up when running RedHat 2.4.16-0.9custom kernel.
  That another machine has, however, IDE disks.

  Earlier experiements with the hanging box used that same RH
  kernel, and hangups were observed there too..

> When the machine is up all the way, and MD disks have finished
> syncing, I execute command:
> 
>   dd if=/dev/zero bs=1024k of=test.file count=8000
> 
> which will lead to hard system hangup where the keyboard won't
> react, SCSI led shines constantly, but nothig happens.
> Right at the moment when the keyboard becomes unresponsibe,
> the disk led will continue to flicker for a few seconds, but
> then the flicker will stop, and the led stays constantly on.

  Of this flicker I am not entirely sure anymore.
  Maybe it happens, maybe not.

  I tried also SGI's  kdb at 2.4.17,  but when the system
  hangs, "pause/break" won't react at all.

> Earlier guestimates of using "noapic", have no effect on
> system hangups.  Same command causes it quite soon. Even
> "noapic nosmp" does hang.
> 
> Large amount of RAM may contribute, but this 3*256MB
> does not need e.g. PAE mode extensions.

/Matti Aarnio