MegaRAID 'Bad Slot' Kernel message and crash.

[Doug Ambrisko]

Tony Byrne writes:
| Basically, after some amount of uptime the kernel will emit a "amr0:
| Bad slot x completed" message and pretty soon after this the box goes into a
| partially unresponsive state forcing us to reboot it.  So far the only
| thing triggering the problem is the nightly jobs, where the amount of
| IO is higher than during the day.
| 
| Before deployment, we tested the box with 5.3-STABLE and managed to
| trigger the problem twice.  This forced us to try 4.10-STABLE which
| was fine in testing and for a number of weeks after deployment.
| However, just before new year we saw our first Bad Slot and crash under
| 4.10.  Since then it has happened 3 more times.  We have upgraded the firmware to
| the latest version available from Intel, and if anything this has made
| the problem worse.
|
| The machine had 3 disks configured as a single RAID5 array.  A fourth
| disk is configured as a hot-standby.  The card is equipped with 128Mb
| of battery-backed cache.  Write-back caching is enabled on the card.
| Read-ahead caching is enabled in non-adaptive mode.
| 
| Is anyone else using a SRCU42X RAID card and seeing similar
| problems to ours?  What about other cards supported by the amr driver?

We run RAID 10 across 4 drives at work on Dell PE2850's which have amr 
RAID's and no-one has reported this problem to me (which they do).  We run
FreeBSD 4.10 & 5.3 on them.  This is with and without our local mods.
We have most experience with 4.10.  Dell has their own firmware version
(atleast to call it is a PERC controller).

For now this is a "works for me".

Doug A.