On Wednesday 21 January 2009 09:13:07 pm Ron Johnson wrote:
If I have lots of existing data in JBODs, would I create a PV and VG
on the new drive, mv all the data from the existing drives to the
new VG, then add my existing drives (while also enlarging the fs) to
the one-drive VG, thus making an uber-device?
That is exactly what I would do. Everyone warns about how cataclysmic things
will happen because your new uber-device has the same failrate as a raid-0
setup, but as long as you backup regularly (perhaps to another LV made from
PV's on different disks) this isn't too much to worry about.
Also, what's a good HOWTO? Everything I've found via Google seems
out-of-date.
When I first set up LVM I used the LVM2 howto here
http://tldp.org/HOWTO/LVM-HOWTO/
The "anatomy" and "common tasks" are really all you need.
Here are the notes I made when I set up LVM. First partition the drives you
want to use. Make sure to set the type of the partitions as linux LVM. Next
tell LVM2 about them with
$ pvcreate <device name>
You can see what devices are seen by lvm2 with pvdisplay. Next make a VG
$ vgcreate <vg name> <device1> <device2> ...
At this point you might need to activate the volume group
$ vgchange -a y <vg name>
Next make a LV in the VG
$ lvcreate -n <lv name> -l <extents> <vg name>
You can get the number of extents available in a volume group with vgdisplay.
There should now be a new device file at /dev/<vg name>/<lv name> that you
can put a filesystem on. You can only enter /dev/<vg name> as root, but the
device-mapper framework puts links to the LV's in /dev/mapper/<vg name>_<lv
name> when you it gets started at boot (this is the location most people
point to in their fstab).