LVM: How to create logical (physical) volume with extent sie 32 Mb

consistgd · 11-13-2006, 05:12 PM

When I installed FC5, the extent size on logical volumes it created was 32M. The I added another hard drive and created another volume group. While I created that, the software formatted partition wih 4M extent, there where no questions asked, so I assume it was by default.

As I undrstand, smaller extend size will allow to use disk space more efficiently, but will make it work slower. How much slower? Is that make sense to reformat it?
Finally: How I can reformat it with extent size defined explicitly?

Thanks.
Gregory

acid_kewpie · 11-14-2006, 09:59 AM

for a normal user you won't see much difference really. if you have *HUGE* disks then you would want a much bigger extent size, but within desktop ranges you'll really not see any difference. you can set an extent sizse with the -L option to lvcreate.

consistgd · 11-14-2006, 11:28 AM

Quote:

Originally Posted by acid_kewpie

for a normal user you won't see much difference really. if you have *HUGE* disks then you would want a much bigger extent size, but within desktop ranges you'll really not see any difference. you can set an extent sizse with the -L option to lvcreate.

Many thanks for the replay!
Is the extent size defined at LV level?
What is the procedure to recreate existing LV?
What if the existing LV contains some data, do I loose it?

acid_kewpie · 11-14-2006, 12:54 PM

oh, my bad, sorry you define a physical extent size at a volume group level, to it'sd the -s option to vgcreate. the lvcreate uses a given number of extent blocks, so it's the size of the LV in terms of the number of extents.

i'm not a guru with LVM to be honest, but i'm fairly sure you would need to formally back up an LV before nuking it and recreating it.

consistgd · 11-14-2006, 05:03 PM

Quote:

Originally Posted by acid_kewpie

oh, my bad, sorry you define a physical extent size at a volume group level, to it'sd the -s option to vgcreate. the lvcreate uses a given number of extent blocks, so it's the size of the LV in terms of the number of extents.

i'm not a guru with LVM to be honest, but i'm fairly sure you would need to formally back up an LV before nuking it and recreating it.

Many thanks for your help. It worked with vgcreate. The only thing confuses me: I had to create LV using GUI program system-config-lvm because I did not find, how to define mout point and "mount after reboot" for a newly created LV. Is that done with mount command separately?

Thanks again.
Gregory