No enough PE per PV

[dev44]

I need to add a 400GB LUN to the volume group. I don't have enough PEs. I am going to reduce the Max PV, but was wondering how to figure out what to reduce it to. I figure if I reduce it to 20 or 30, I should have enough but is there a way to calculate what I can bring it down to and still have my Max PV as high as possible?

Thanks,

[Torsten.]

Can you post a "vgdisplay -v" for this VG?

[Duncan Edmonstone]

Are you talking about using vgmodify to change the max per per pv in a VG? Od so there's a sort of preview option which shows you possible configurations - I think its 'vgmodify -t '.

See this whitepaper for details:

http://h20000.www2.hp.com/bc/docs/support/SupportManual/c01920387/c01920387.pdf (BSC link updated by admin)

Or are you talking about something else?

HTH

Duncan

[James R. Ferguson]

Hi:

If you are running 11.23 or 11.31, then Duncan's link to 'vgmodify' and/or the 11.31 manpages will enable you to calculate a value.

If you are running 11.11 (or earlier) see Technical Knowledge Base # emr_na-c01037913

There in are tables of maximum max_pe values for various disk configurations.

Regards!

...JRF...

[dev44]

Sorry, I completely forgot to add the vgdisplay:VG Name /dev/vgXX
VG Write Access read/write
VG Status available
Max LV 255
Cur LV 29
Open LV 29
Max PV 144
Cur PV 4
Act PV 4
Max PE per PV 14076
VGDA 8
PE Size (Mbytes) 16
Total PE 41907
Alloc PE 40219
Free PE 1688
Total PVG 0
Total Spare PVs 0
Total Spare PVs in use 0

I do plan on using vgmodify.

[Torsten.]

Still not sure about your OS version (uname -a)?

I wonder about this:

Max PV 144
Cur PV 4


Do you really plan to add 140 disks to this VG?

[dev44]

HP-UX 11.23

No we don't plan on 144 disks....but I would like to figure out/calculate how many free PEs I would have if I brought that number down to say 20 or 30.

[Rasheed Tamton · Accepted solution]

Your real issue is that your Max PE per PV (14076). The PE Size is 16 MB. So you can only use a LUN size of 220GB (14076*16=225216), even if you present a 400GB LUN to the system.

So, you need to modify the Max PE per PV to 25600 (25600*16=409600) in order to use a 400GB LUN. In future, if there is a requirement for higher size LUNs, then increae Max number of PEs to yet higher value (32000 for 500GB LUN).

man vgmodify (read it carefully)

Regards.

[Torsten.]

Maybe I don't understand ... but MAXPV and FREEPE is not directly related.

PV physical volume (= disk or LUN)

Max PV 144
Cur PV 4

Now you have 4 disks (LUNs)

Max PE per PV 14076
PE Size (Mbytes) 16

Total PE 41907

You have a total of 670GB.

Alloc PE 40219
Free PE 1688

27GB are still free and unassigned.

[dev44]

HP-UX 11.23

No we don't plan on 144 disks....but I would like to figure out/calculate how many free PEs I would have if I brought that number down to say 20 or 30.

Sorry if I take a long time to respond but I am getting errors every time I post, that's if it posts at all! Very frustrating.....

[Torsten.]

Now I got it too ;-)
I was totally focused on that max PV (what doesn't make sense - that worries me), but it should be max **PE**!

Thanks Rasheed ...


If you read the manual now, make sure you follow all the steps (including preview of command execution)!

[dev44]

Here is my error:
vgextend: Warning: Max_PE_per_PV for the volume group (14076) too small for this PV (25599).
Using only 14076 PEs from this physical volume.

I got this before on another server and since I cannot up the size of the PE from say 16 to 32, I was able to change the MAX PV and that worked....it gave me enough PEs.

[dev44]

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_PEs.

[Torsten.]

Do you have still the wrong direction?

You need to increase the

MAX_PE per PV

Example:

# vgmodify -e 25600 vgXX



Make sure you DECREASE the max_PV from 144 to a smaller value - you don't need this high value!

[dev44]

Ok, I think I've got it. In order to bump up the Max PE per PV, I have to drop the max PV. I was able to run vgmodify with "-r" to test and it looks like it will work.

root:/home/root$ vgmodify -r -p 50 -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
The current and new Volume Group parameters differ.
An update to the Volume Group IS required


New Volume Group settings:
Max LV 255
Max PV 50
Max PE per PV 32000
PE Size (Mbytes) 16
VGRA Size (Kbytes) 13024
Review complete. Volume group not modified

[Torsten.]

max_pv of 50 may still be overkill, but anyway - if this works it is ok.

I'm sure you will solve this now.

Good luck!


Please don't forget to read

http://forums12.itrc.hp.com/service/forums/helptips.do?#33

[Rasheed Tamton]

Yes. You can decrease the no. of PVs, if you plan to use 500GB LUNs. Anyway the parameter are ok but the no. of PVs up to you to decide.

Thanks Torsten.

[dev44]

Thanks very much for all the advice folks!