On 13.09.2012 08:31, Eugene Grosbein wrote:
9-STABLE has got options GEOM_RAID in GENERIC.
In real world, this change is pretty harmful and there are lots of cases
when 9.0-RELEASE systems upgraded to 9-STABLE fail to mount root UFS filesystem
or attach ZFS.
It seems, there are lots of HDDs supplied with pseudo-RAID labels at the end:
pre-installed Windows machined having motherboards with pseudo-RAID
like Intel RapidStore and alike. One can not even be aware of these labels.
9.0-RELEASE can be installed on such HDDs and use them with GMIRROR or ZFS
without a problem. Upgraded to 9-STABLE, such system fails to build due
to GRAID jumping out of box and grabbing HDDs for itself,
so GMIRROR or ZFS got broken.
That's makes users very angry when production server fails to boot
with GENERIC kernel after correctly performed upgrade.
GEOM_RAID compiled in GENERIC should be deactivated and require activation
with some loader knob. Also, we need distinct RELEASE NOTES warning about the
issue.
Problem of on-disk metadata garbage is not limited to GEOM_RAID. For
example, I had case where remainders of old UFS file system were found
by GEOM_LABEL and ZFS incorrectly attached to it instead of proper GPT
partition, making other partitions inaccessible. Does it mean we should
remove GEOM_LABEL also? I don't think so. All what GEOM_RAID is guilty
in is that it was not in place for 9.0 release. If we remove it now, it
will just postpone the problem for later time or will never be able to
add it again because of the same reasons.
Unlike GEOM_LABEL, metadata of GEOM_RAID is quite easy to delete without
complete disk erase: `graid status -ag`, `graid delete ...`. Yes, it can
be a problem if system can't boot, but now we at least have live mode on
installation images, that should allow to do it.
Adding some loader tunables indeed could simplify recovery in case of
boot problem. I will probably add such ones now. It won't hurt. But I
disagree they should be disabled by default, limiting users who really
want to use BIOS RAID. Disabling them will also make metadata removal
without full wipe more difficult because different RAIDs have different
on-disk metadata layout, and you should know where exactly to apply dd.
--
Alexander Motin
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