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LVM + RAID follow up

On Tue, Nov 07, 2006 at 03:32:01PM -0500, Derek Atkins wrote:
> I think that makes sense...  So I build the MD devices from the
> physical drives/partitions and then layer LVM on top of that to build
> the actual filesystem "partitions".


/dev/sda3 + /dev/sdb3 = /dev/md0  through RAID

/dev/md0 => /dev/mapper/root => /
            /dev/mapper/home => /home
	    /dev/mapper/var  => /var
	    /dev/mapper/swap => swapspace

through LVM and mount.

> Man, this is just confusing..
> I would think that after a while you'd have a LOT of MDn devices..
> and eventually you wind up in this similar situation where you're
> breaking down your drives into many "small" partitions.

After a while, you note that you have n 2TB drives and it's time
to realign everything. You do a backup, just in case. Then you
tell the RAID system to remove a drive. That gets repartitioned
into a tiny part and a huge part. When you have enough of those,
you tell the RAID that it's a decayed RAID. Create new LVM
partitions. Copy over the old data, LVM partition by LVM
partition. Remove the remaining drives from the old RAID,
repartition them and restore them as part of the new RAID. Let
it rebuild.

> Do you?  If I assume that the RAID5 is all one partition, then if the
> partition size increases I can just run resize2fs to increase the size
> of the file system.  The only question is the RAID5 parts, will it
> be able to build a filesystem out of a 3x400GB + 3x800GB partition?

Each partition for RAID must be the same size.


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