Re: [gentoo-user] LVM Migration Example (was: Advice about setting up split home directory)

[Josh Cepek]

Norberto Bensa wrote:
> Quoting Josh Cepek <josh.cepek@×××.net>:
>> 3) You can easily migrate between hard drives while the system is
>> online by moving LV's from one Physical Volume (PV) (eg: a hard disk)
>> to another.
>
> --!!
>
> Have you ever tried that? I've almost killed both hard drives doing an
> on-line migration to a bigger HD. I wouldn't recommend it.

Actually, yes, and with fairly decent results.  You are right that his 
process will take quite a while on large LV's, and doing other 
disk-intensive operations at the same time will bring the system to a 
crawl.  However, I used this technique to remove an old NTFS partition 
when I migrated to a VM for my Windows system.

To recover the space into a single larger PV (a single PV was important 
for me here) I attached an external USB 2.0 drive, created a PV, and 
added it to my pre-existing VG.  I then pvmove-ed the data over to the 
external drive, removed the old partitions, and re-created a single 
larger partition on the internal drive.  Once the LV's were migrated 
back I removed the PV on the external drive.

In my case I also moved my non-LVM root partition to the end of the 
drive after the migration to the external drive, but had I not needed to 
do this I could have performed the entire operation without needing to 
even reboot.

All in all I think this example demonstrates the utter flexibility you 
get with LVM.  I leave it up to each user to determine where flexibility 
ends and insanity takes over ;)


-- 
Josh