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Re: Problems/workarounds for install to root on LVM on RAID

A rather serious problem I encountered when running LVM on RAID is that as
of a few days ago, RAID wasn't automatically activated on startup.  This
caused LVM to find its partitions inside the RAID partition and mount one of
those.  This is obviously a horrible thing to do as it breaks your RAID
mirroring and thus you end up with a corrupt RAID device when you do bring
it up.  Although if you know what you are doing and what happened you could
probably recover from it.  The lvm lists say you need to put an exclusion in
the device section lvm config for the underlying partitions or drives that
make up the raid device.  There is suppose to be a patch floating around on
the lvm list to automatically skip partitions that have a partition type of
raid autodetect as the default behavior.

I also had problems when deleting and re-adding lvm and raid partitions.  It
tended to cause lockup in 35dump.  Sorry, don't have any logs of that.

I also tried lvm on raid with a 2.6 kernel but pvscan just ran forever and
kept growing in memory size.  It had over 400MB of memory when I killed it.

A small problem I encountered is if you create 2 logical partitions in your
lvm volume that are the same size and are right next to each other, you
can't edit the second one without setting up the first.  If you select the
second one it will just throw you into the first one.  That wouldn't
normally be a problem as you generally setup all the partitions, but I had
my root partition and tmp partition the same size, but was leaving the root
partition alone because I couldn't get it to work in the lvm on raid
configuration.  So just a small bug in partman...

The raid device also shows it only being 2.0 GB in size when the partition
underneath it is 79GB.

This was all on the 20040524 build.

Josha Foust

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