* [linux-lvm] Query on PE size
@ 2013-06-05 2:07 Kumar amit mehta
2013-06-06 9:37 ` Zdenek Kabelac
0 siblings, 1 reply; 2+ messages in thread
From: Kumar amit mehta @ 2013-06-05 2:07 UTC (permalink / raw)
To: linux-lvm
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
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [linux-lvm] Query on PE size
2013-06-05 2:07 [linux-lvm] Query on PE size Kumar amit mehta
@ 2013-06-06 9:37 ` Zdenek Kabelac
0 siblings, 0 replies; 2+ messages in thread
From: Zdenek Kabelac @ 2013-06-06 9:37 UTC (permalink / raw)
To: LVM general discussion and development; +Cc: Kumar amit mehta
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
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