[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]

Re: [linux-lvm] Query on PE size



Dne 5.6.2013 04:07, Kumar amit mehta napsal(a):
Hi,

I see that a VG will set the default PE size to 4MiB, i.e.
4 * 1024 * 1024 = 4194304
(Please correct me if I'm wrong)

<snip>
# pvcreate /dev/vdc1
# vgcreate testvg /dev/vdc1
# vgdisplay
# vgdisplay testvg|grep "PE Size"
    PE Size               4.00 MiB <----
<snip>

I see that :
vgcreate()
  -->vgcreate_params_set_defaults()
    -->vp_def->extent_size = DEFAULT_EXTENT_SIZE * 2;

Where DEFAULT_EXTENT_SIZE is #defined to 4096
<snip from lib/config/defaults.h>
#define DEFAULT_EXTENT_SIZE 4096        /* In KB */
<snip from lib/config/defaults.h>

This means that the default extent size being set is 8192, but as mentioned
earlier,the default extent size as reported by 'vgdisplay' is 4 MiB. So Can
someone please point me to the place where this conversion of 8192 into 4MiB
is taking place in the code ?

Variables in the lvm source code which have suffix _size should keep the size in 512b block units -> 8192 * 512b block => 4MiB

Zdenek


[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]