Query on PE size
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 ?
-Amit
Dne 5.6.2013 04:07, Kumar amit mehta napsal(a):
Quoted 24 lines
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_SIZEis #defined to 4096
<snip fromlib/config/defaults.h>
#defineDEFAULT_EXTENT_SIZE4096 /* In KB */
<snip fromlib/config/defaults.h>
Quoted 4 lines
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