max pe per pv

[newunix]

what is max PE per PV. and why it is used for.

how max PE per PV is related to PE.

[Michal Kapalka (mikap)]

hi,

i would recommend to read this docu :

" HP-UX LVM Supported Limits "

http://bizsupport2.austin.hp.com/bc/docs/support/SupportManual/c02019992/c02019992.pdf

mikap

[vishnu.khandare]

Hi,

When a volume group is created , the physical volume added to it is divided into several smaller logical pieces Know as Physical Extents(PE).

The default size of PE is 4MB which can be set between 1 to 256MB

Max PE per PV can be 65535 in version 1 VG
Max PE per PV can be 16777216 in version 2 and 2.1 VG

Please refer below link,

http://www.docstoc.com/docs/27220396/HP-UX-11i-V3-LVM

Hope all ur queries resolved
Don't forget to assign points

Regards
Vishnu Khandare

[SoorajCleris]

Hi,

The query is explained above.

Addon==>

This parameter put you in to trouble if you are using 11.11.

If you have created a VG with disk which have smaller disk size, later you will be able to utilize up to that size only even if you add a disk in more size.

for example, if you use 4.3GB disk to create the volume group, and later if you add 10GB disk, you will be able to utilize only 4.3 GB of the new disk.

The parameter is defined while creating the VG and you will be never able to change that untill and unless you recreate it.

:)

Regards,
Sooraj

[SoorajCleris]

Hi,

in 11.23 and 11.31 you have an option to change this using "vgmodify".

Regards,
Sooraj

[P Arumugavel]

hi,

to say simply, maximum number of physical extents that can be allocated from any of the physical volumes in the volume group....

Rgds \ vel

[newunix]

hi

for example, if you use 4.3GB disk to create the volume group, and later if you add 10GB disk, you will be able to utilize only 4.3 GB of the new disk. -------------------->

suppose i am creating a new vg from 10 gb disk allocated .

vgcreate /dev/dsk/c1t2d0

so that pe size will be 4 and max pe per pv will be 1010.

now i am adding another pv to the vg and extending it.

after adding pv,do my PE value gets increased???

[Kapil Jha]

Lets make it simple,

PE value can not change untill you make the delete and create VG again.

max_pe_per_pv you can change with unsupported vgmodify utility.

If you add a disk normally you can only use the maximum [pe*max_pe_per_pv]MB space on newly added disk, doesn not matter how big it is.


http://forums11.itrc.hp.com/service/forums/questionanswer.do?threadId=1224820

this would help you understand.

BR,
Kapil+

[newunix]

root:/home/root$ vgmodify -r -e 32000 vgxxx

Current Volume Group settings:
Max LV 255
Max PV 144
Max PE per PV 14076
PE Size (Mbytes) 16
VGRA Size (Kbytes) 16368
vgmodify: VGRA for the disk is too big for the specified
parameters. Decrease max_PVs and/or max_PE


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

it asked to reduce the max pv and max pe,

y it is need to reduce the max pv????

[Hein van den Heuvel]

> it asked to reduce the max pv and max pe,
> y it is need to reduce the max pv????

You need to do this to make more PE's available per PV.

The total number of PE's, and the size of each PE is declared when the volume group is created and can not be changed.


All the useable disk space needs to be mapped by a PE.

So the minimum for MAX_PE_PER_PV is that is needs to be as big as your biggest PV divided by the PE size. That's possibly less than 32000.
The maximum of MAX_PE_PER_PV is defined by MAX_PE_PER_PV times MAX_PV which is constant.
So to get a twice as big MAX_PE_PER_PV, you must divide MAX_PV by two.

MAX_PV is 144. Is that realistic for your situation? I suspect not. Let's say 20 is all the PV's you'll ever need for this VG.
Well, that's 7x smaller so you can use 7x more PE's per PV without re-creating the VG.

Cheers,
Hein.


The MAX_PE_PER

[newunix]

vgdisplay -v testdir
--- Volume groups ---
VG Name /dev/testdir
VG Write Access read/write
VG Status available, exclusive
Max LV 255
Cur LV 1
Open LV 1
Max PV 16
Cur PV 2
Act PV 2
Max PE per PV 3071
VGDA 4
PE Size (Mbytes) 16
Total PE 4350
Alloc PE 4350
Free PE 0
Total PVG 0
Total Spare PVs 0
Total Spare PVs in use 0
VG Version 1.0
VG Max Size 786176m
VG Max Extents 49136

--- Logical volumes ---
LV Name /dev/testdir/lvoltest
LV Status available/syncd
LV Size (Mbytes) 69600
Current LE 4350
Allocated PE 4350
Used PV 2


--- Physical volumes ---
PV Name /dev/disk/disk116
PV Status available
Total PE 3071
Free PE 0
Autoswitch On
Proactive Polling On

PV Name /dev/disk/disk382
PV Status available
Total PE 1279
Free PE 0
Autoswitch On
Proactive Polling On


>diskinfo /dev/rdisk/disk382
SCSI describe of /dev/rdisk/disk382:
vendor: HP
product id: HSV210
type: direct access
size: 20971520 Kbytes
bytes per sector: 512

>diskinfo /dev/rdisk/disk116
SCSI describe of /dev/rdisk/disk116:
vendor: HP
product id: HSV210
type: direct access
size: 50331648 Kbytes
bytes per sector: 512


max pe per pv =3071
pe size=16.

max pe per pv * pe = 49316 ( appro 49 gb )

max pe per pv * pe size * max pv =786176(767 gb)

total disk allocated to vg is nearly 70 gb.

but vg can hold only max of 49 gb,, and disk space more than that will not be considered.

but we have added 70 gb disk to that vg.

so plz suggest for above comments if i am wrong.
if its correct how can we proceed to that..

[Hein van den Heuvel]

the numbers seem to add up.
But you had

Max PV 144
Max PE per PV 14076

Now you have

Max PV 16
Max PE per PV 3071

What happened there? Which commands?
Decreasing the Max PV should have allowed you to increase Max PE.

Was that knob turned the wrong way?
retry that : vgmodify -r -e 32000 vgxxx ?

Hein.

[newunix]

hi hein

Max LV 255
Max PV 144 its a link post from kaphil , after reading post i got doubt.

the latest vgdisplay is my post,, can u advice it for testdir vg.

[Hein van den Heuvel]

Ah, yes, not I see the 'quotation'.
Your VG may have been configured with too many restrictions.
You may want to re-create, or jsut add new PV's to a fresg new VG. Why not?
Or you can lower MAX PV still futher.
How many PV's do you expect? 16? ... 4?
Lower to 4 and increase max PE ?

Hein

[newunix]

hi

my doubt is whether full disk space in vg is used now or not..

[SoorajCleris]

Hi,

No need to make this so complicated.

Max PE per PV is for one PV

Total PE can allocate to VG is not max PE per PV but

"Max PE per PV" x Number of PVs

2) the maximum size utilized from any disk will be "Max PE per PV" x PE size.

this is vg wide parameter and not specific to any PVs ,

simply multiply and calculate what you have and decide.

3) Please refer the link below.
http://forums11.itrc.hp.com/service/forums/helptips.do?#28

Regards,
Sooraj

[P Arumugavel]

Hi,

You got into more complex.
Lets see simple.

Only applicable to volume groups version 1.0.
The default value for max_pe is 1016. However, if the size of
any physical volume exceeds 1016 times the pe_size , the default value for
max_pe is adjusted to match the physical volume size. The maximum number
of physical extents can be a value in the range 1 to 65535, 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) for volume groups version
1.0.

So your disk with value of upto 255.99GB (4*65535) can be utilised fully without changing any outline value as the default value for max_pe is adjusted with default pe_size value of 4MB to match the physical volume size. If the disk size exceeds more than this value 4*65535MB, then you will not have the whole size to utilize. Here the scenario need you to change the value of either max_pe or pe_size, else both to adjust to match the disk size.

Simple ideas simply work better...

Reg \Vel

[Raghunandan Pancholi]

if u want u can assign full space of your hard disk.or u can extend it in future as per requiremt.max PE is depend on user to user or based on the space of your hard drive .