PE and LE

[newunix]

what is PE and LE in lvm..

can u plz explain me in detail..

as for i read the docs

PE should be equal to LE,,, this should be same in all condition or not.

can i have a clear idea about tat

[James R. Ferguson]

Hi:

PE = Physical Extent
LE = Logical Extent

An "extent" is a unit of allocation. For a logical volume that is unmirrored, there is a 1:1 PE:LE ratio. If you use LVM mirroring for a logical volume then you might see 2:1 PE:LE or 3:1 PE:LE.

That is, there are *copies* of the logical extents on (by default) different physical volumes.

LVM mirroring is done at the *logical volume* level. See the 'lvm(7) manpages for some fundamental concepts.

Regards!

...JRF...

[Michael Steele_2]

Hi

Physical extents fill up the physical volume - default 4 MB
Logical extents fill up the logical volume - Default 4 MB
An LE is written into ram
A PE is written onto the pv
When the LE is 'flushed' out of RAM the PE is written to disk
Both extents are filled with file system blocks of data - default size 1024 bytes.
You can fill a 4MB extent with 4096 blocks of data.

[newunix]

suppose if i want to create another lv in the same vg ,,, what is the maximum and minimum extent can I use

---------------------------------------------

volume group


VG Name /dev/vg254
VG Write Access read/write
VG Status available, exclusive
Max LV 255
Cur LV 1
Open LV 1
Max PV 16
Cur PV 1
Act PV 1
Max PE per PV 1016
VGDA 2
PE Size (Mbytes) 32
Total PE 255
Alloc PE 255
Free PE 0
Total PVG 0
Total Spare PVs 0
Total Spare PVs in use 0
VG Version 1.0
VG Max Size 508g
VG Max Extents 16256

--- Logical volumes ---
LV Name /dev/vg254/lvolindexDE
LV Status available/syncd
LV Size (Mbytes) 8160
Current LE 255
Allocated PE 255
Used PV 1


--- Physical volumes ---
PV Name /dev/disk/disk360
PV Status available
Total PE 255
Free PE 0
Autoswitch On
Proactive Polling On


root @ cdd :/>pvdisplay /dev/disk/disk360
--- Physical volumes ---
PV Name /dev/disk/disk360
VG Name /dev/vg254
PV Status available
Allocatable yes
VGDA 2
Cur LV 1
PE Size (Mbytes) 32
Total PE 255
Free PE 0
Allocated PE 255
Stale PE 0
IO Timeout (Seconds) default
Autoswitch On
Proactive Polling On

root @ Cdd :/>v^? lvdisplay -v /dev/vg254/lvolindexDE
--- Logical volumes ---
LV Name /dev/vg254/lvolindexDE
VG Name /dev/vg254
LV Permission read/write
LV Status available/syncd
Mirror copies 0
Consistency Recovery MWC
Schedule parallel
LV Size (Mbytes) 8160
Current LE 255
Allocated PE 255
Stripes 0
Stripe Size (Kbytes) 0
Bad block on
Allocation strict
IO Timeout (Seconds) default

--- Distribution of logical volume ---
PV Name LE on PV PE on PV
/dev/disk/disk360 255 255

--- Logical extents ---
LE PV1 PE1 Status 1
00000 /dev/disk/disk360 00000 current
00001 /dev/disk/disk360 00001 current
00002 /dev/disk/disk360 00002 current
00003 /dev/disk/disk360 00003 current
00004 /dev/disk/disk360 00004 current
00005 /dev/disk/disk360 00005 current
00006 /dev/disk/disk360 00006 current
00007 /dev/disk/disk360 00007 current
00008 /dev/disk/disk360 00008 current
00009 /dev/disk/disk360 00009 current
00010 /dev/disk/disk360 00010 current
00011 /dev/disk/disk360 00011 current
00012 /dev/disk/disk360 00012 current
00013 /dev/disk/disk360 00013 current
00014 /dev/disk/disk360 00014 current
00015 /dev/disk/disk360 00015 current
00016 /dev/disk/disk360 00016 current
00017 /dev/disk/disk360 00017 current
00018 /dev/disk/disk360 00018 current
00019 /dev/disk/disk360 00019 current
00020 /dev/disk/disk360 00020 current
00021 /dev/disk/disk360 00021 current
00022 /dev/disk/disk360 00022 current
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00024 /dev/disk/disk360 00024 current
00025 /dev/disk/disk360 00025 current
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00027 /dev/disk/disk360 00027 current
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00100 /dev/disk/disk360 00100 current
00101 /dev/disk/disk360 00101 current
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00110 /dev/disk/disk360 00110 current
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00119 /dev/disk/disk360 00119 current
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00210 /dev/disk/disk360 00210 current
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00230 /dev/disk/disk360 00230 current
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00253 /dev/disk/disk360 00253 current
00254 /dev/disk/disk360 00254 current

[Torsten.]

There are no free PEs, so you cannot create another LV.

[Durvesh Mendhekar]

Hi,

Add PV to your VG and then try to create a LV into it.

Refer attahed document.

Durvesh

[R.K. #]

Hello..

VGDISPLAY ahs a lot of information
# vgdisplay -v

Total PE 255
Alloc PE 255
Free PE 0 <<<<

So you have no free PE left in your VG, hence you have to add a disk to before you can create an LV.

[Matti_Kurkela]

vgdisplay output:
> PE Size (Mbytes) 32

The extent size of a VG is defined at VG creation time, so even if you add a new disk to your vg254, it would use the same extent size.

Even the vgmodify command cannot change the extent size of an existing VG: if you need to change the extent size, you must create a completely new VG and copy the data over to it.

Your VG name "vg254" suggests you have a lot of volume groups. You might wish to read about LVM v2.x, a new feature of HP-UX 11.31 March 2008 and later releases:

http://docs.hp.com/en/lvm-v2/L2_whitepaper_8.pdf

You should also read the LVM Limits whitepaper:

http://docs.hp.com/en/6054/LVM_Limits_White_Paper_V4.pdf

MK

[newunix]

so Matti

what u mean is eventhough if i add a disk to that particular vg ,,, i have to recreate the vg and restore the data back to it..

but i have pe size in 32

and max pe per pv is 1016 from the above output

so i have disk up to 31 gb appro( 32 * 1016 )

is it necessary to use vbgmodify cmd here

[newunix]

hi

just now i am in to unix and steped in to lvm..

reply me for the last post.

if i am correct or not