topic Re: What sets PE size in Operating System - HP-UX

What sets PE size

dictum9 — Thu, 18 May 2006 10:59:29 GMT

When you do vgdisplay, you see the line

PE Size (Mbytes) 16

sometimes it can be 4 or 8. What controls this? I see no option to set PE size in pvcreate.

Re: What sets PE size

someone_4 — Thu, 18 May 2006 11:05:05 GMT

Hi

It will be with
vgcreate the -s options

-s pe_size Sets the number of megabytes in each physical
extent, where pe_size is expressed in units
of megabytes (MB) in the range 1 to 256.
pe_size must be equal to a power of 2 (1, 2,
4, 8, etc.). The default value for pe_size
is 4 (four megabytes).

Re: What sets PE size

Uday_S_Ankolekar — Thu, 18 May 2006 11:07:22 GMT

vgcreate will take care of this. Read man pages for vgcreate

-USA..

Re: What sets PE size

Matti_Kurkela — Thu, 18 May 2006 11:14:53 GMT

It can be set when you create a volume group, and only then.

One extent is the smallest piece of disk you can (theoretically) present to the applications as a logical volume.

When you create a volume group, you decide the maximum number of extents, the extent size and the maximum number of physical volumes in the volume group. These three things determine the size of the LVM configuration data for that volume group.

Because all disks in a volume group must have the same extent size, there is no point to set PE size in pvcreate.

Re: What sets PE size

dictum9 — Thu, 18 May 2006 11:17:50 GMT

OK.

Another question I have, I have a HP 73.4G disk.

However in the vg00 volume group info, (the only volume group I have):

Total PE 4318
PE Size (Mbytes) 16

Which means I have 69088 MB on that disk.

However, diskinfo reveals it has 73.4GB or 75161.6 MB, or a difference of 6073 MB. Where did that 6GB go? Has it gone to another "slice" (this is an Itenium machine) or has it gone for filesystem creation?

Re: What sets PE size

Deoncia Grayson_1 — Thu, 18 May 2006 11:46:26 GMT

could you do a bdf?

I belive it has gone to your filesystem creation, also is your vg00 mirrored?

Re: What sets PE size

Jeff Schussele — Thu, 18 May 2006 12:22:15 GMT

Yes - Itanium boot disks have 3 slices.

#1 is the FAT-32 slice used for booting
#2 is the standard LVM slice for the OS
#3 is the Diag slice used for Offline Diags.

So the vgdisplay of vg00 is only going to show you the size of slice #2

HTH,
Jeff

Re: What sets PE size

dictum9 — Thu, 18 May 2006 12:54:50 GMT

That clarifies a lot.

Re: What sets PE size

Nguyen Anh Tien — Thu, 18 May 2006 21:45:45 GMT

vgcreate has some important option that is usually used in creating VG.
#vgcreate -s PE_SIZE -e MAX_PE
PE_SIZE can be: 8,16,32,64...
Max_pe is number you can specify to address all you disk's capacity
Eg: You want to create 01 VG contains 02 73GB disk with PE=16 so MAX_PE=>73*2=146GB*1024/16MB=9344
HTH