LVM + RAID follow up

[richb at pioneer.ci.net (Rich Braun)]

John Abreau asserted:
> Like I said before, in the LVM layer you can add the new md device
> to the PV, slide the filesystem transparently from the old md device
> to the new one, and then remove the old md device from the PV.

At the risk of flogging this thread further into submission than it's already
been... Reading your sequence of commands, I'm still wondering how your
approach achieves the goal of consolidating md devices.  Let's take the simple
case of upgrading a four-disk configuration of 400GB drives to a four-disk
configuration of 1TB drives.  You start out 90% full, on a volume of 1.2TB
available, set up as a RAID1 /dev/md0 (boot, just 200MB) and a RAID5 /dev/md1.
 You want to wind up with the same two md devices on your new drives, with as
few time-consuming data transfers as possible.

I gather what you're suggesting is to install the new drives simultaneous with
the old, and issuing the commands you've cited to do a single transfer of each
of the two md devices, then pulling the old drives?  Sounds like a pretty
powerful argument in favor of LVM.

-rich


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