[linux-lvm] Mirrored LV
jbrassow at redhat.com
Sat Sep 20 03:39:52 UTC 2008
Just to answer some questions:
You can use just 2 disks to create a mirror and a disk log:
prompt> lvcreate --alloc anywhere -m1 -L 500M -n my_lv my_vg
I wish the allocation policy 'normal' (which is the default) would
also do this... but instead you must choose a looser allocation policy
to get what you want.
The reason that you want the disk-based log is to prevent all the
extra work when you machine comes up.
The reason that LVM wants a separate disk for the log is so the head
on the storage device doesn't need to go ping-ponging around the
device. (The log is touched for almost every write.) So, its a
performance thing... and possibly a not-wear-out-your-hardware thing
It won't matter if the master disk with the log dies. Your mirror
will simply become a linear device composed of the last remaining disk
On Sep 19, 2008, at 5:01 PM, Koen Vermeer wrote:
> Op vrijdag 19-09-2008 om 10:31 uur [tijdzone -0700], schreef
> malahal at us.ibm.com:
>> It needs it own PV. Create an extra partition on your master disk and
>> add the PV tou the volume group. Then run lvcreate again with out
>> corelog option. By default the command would create a disklog. You
>> also specify where you want your log.
> OK, did that! I guess I need one additional partition for each volume
> group, then.
> Now, what happens if the master disk (which includes the log) dies?
> Won't LVM complain that it cannot find the log? I'm not saying I
> it too, but with this stuff I guess it's better to be safe than sorry!
> linux-lvm mailing list
> linux-lvm at redhat.com
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
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