Re: raid10,f2 Add a Controller: Which drives to move?

[Michael McCallister <mike@mccllstr.com>]

Tomáš Dulík <dulik <at> unart.cz> writes:
> I am not sure if I understand your question, but I suppose you will hit 
> the problem of udev naming of your disks, and if your disks are 
> hotswap-able, then also the problem of hotswap, which is currently 
> discussed here in this mailing list.

Thanks for the heads up.  I did the swap while powered down and only brought the
system up using an Ubuntu Live CD, so the udev on my current root partition
didn't come into play.  During that live-CD boot, I had no apparent problems
with the changing device names.  They had changed pretty significantly: sdb
became sdd, sdc became sdb, sdd became sde, and another device not part of the
array became sdc.  In spite of the shuffle and a new SATA controller, mdadm was
able to reassemble the RAID devices on those drive partitions with no input from
me.  I believe this is because mdadm scanned the partitions looking device for
the appropriate UUIDs in the metadata, and with all the devices accounted for,
it was able to "do the right thing".  I was very impressed.

When I boot using the original root partition (running Ubuntu Hardy), maybe udev
will shuffle the device names more severely.  But so long as mdadm is configured
to scan all the available partitions, I expect it will locate all the pieces,
whatever they may be named, and successfully reassemble the arrays.


Mike


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