Extending a vg of multiple LUNS from an EVA?

[Pete Hakesley]

Hi,

I have inherited a system where the volume groups are made up of chunks of 25GB to make much larger file systems. I was wondering does anyone know it is possible to add new LUNS to this vg anduse lvextend etc to increase the vg size without having to rebuild the whole logical volume.

Example: Currently 250GB made up of 10x25G LUNS. Developer now want the file system to be 400GB.

Thanks in advance.

[Sandman!]

The default value for Max PV is 16 so you can add 6 more PVs (25 GB ea.) to your VG for a total of 16 LUNs X 25 GB = 400 GB.

[Ludovic Derlyn]

hi

for me, if i have well understood, you have need to increase space disk of vg from 250 to 400

for me , you must add new Lun, and this lun will be added to vg

Check if vg , maximal pv allowed (max pv) and size of disk authorized (max pe par pv and pe size)

regards

[Torsten.]

It depends.
If the LVOLs are striped across the "physical disks" (vdisks), you will have a problem when extending the LVOLs.
But to vgextend the VG to new vdisks should not be a problem.

Just in case you have 11.23 or 11.31 you may consider to expand the current vdisks. You can use "vgmodify" to adjust the LVM config.

[Sandman!]

Ofcourse it might help if you attached the output of vgdisplay on the target VG in case your lvol is striped or mirrored or both i.e.

# vgdisplay -v

~cheers

[Court Campbell]

I think you would better off creating a new volume group with 2 - 200GB luns and copying the data over. I never really understood creating a lot of small disks on a device like the eva. Probably not not what you want to hear. And if you try to add larger disks you will more than likely get hosed by the Max PE per PV.

[Court Campbell]

I guess I could have mentioned needing to have to create new lvols also.

[Ninad_1]

In addition to (some points may be repeating) what others have suggested -
you need to check the following things -
1. Max PV for the VG should be equal or more than the total number of disks (PVs) present in the VG + the total number of disks (PVs) that you wish to add (extend VG with)
2. PE size - this is very important if you want to extend your filesystem - the max volume size you can have is 65535 * PE size [ Thus in your case if PE size is 4 MB, then you cannot extend your logical volume beyond around 255 GB]
3. Max PE per PV - since your initial disks are all 25 GB - your Max PE per PV would be around (25 GB / PE Size) , thus even if you add a larger size disk, the maximum space you can use from this disk would be PE size * Max PE per PV = which again is almost = 25 GB.

Hope this clarifies,
Ninad

[Pete Hakesley]

Output of vgdisplay

--- Volume groups ---
VG Name /dev/vguat
VG Write Access read/write
VG Status available
Max LV 255
Cur LV 1
Open LV 1
Max PV 16
Cur PV 15
Act PV 15
Max PE per PV 3199
VGDA 30
PE Size (Mbytes) 8
Total PE 47985
Alloc PE 47985
Free PE 0
Total PVG 0
Total Spare PVs 0
Total Spare PVs in use 0

--- Logical volumes ---
LV Name /dev/vguat/lvol1
LV Status available/syncd
LV Size (Mbytes) 383880
Current LE 47985
Allocated PE 47985
Used PV 15


--- Physical volumes ---
PV Name /dev/dsk/c12t0d0
PV Status available
Total PE 3199
Free PE 0
Autoswitch On

PV Name /dev/dsk/c12t0d1
PV Status available
Total PE 3199
Free PE 0
Autoswitch On

PV Name /dev/dsk/c12t0d2
PV Status available
Total PE 3199
Free PE 0
Autoswitch On

PV Name /dev/dsk/c12t0d3
PV Status available
Total PE 3199
Free PE 0
Autoswitch On

PV Name /dev/dsk/c12t2d4
PV Status available
Total PE 3199
Free PE 0
Autoswitch On

PV Name /dev/dsk/c12t2d5
PV Status available
Total PE 3199
Free PE 0
Autoswitch On

PV Name /dev/dsk/c12t2d6
PV Status available
Total PE 3199
Free PE 0
Autoswitch On

PV Name /dev/dsk/c12t2d7
PV Status available
Total PE 3199
Free PE 0
Autoswitch On

PV Name /dev/dsk/c12t3d0
PV Status available
Total PE 3199
Free PE 0
Autoswitch On

PV Name /dev/dsk/c12t3d5
PV Status available
Total PE 3199
Free PE 0
Autoswitch On

PV Name /dev/dsk/c12t3d6
PV Status available
Total PE 3199
Free PE 0
Autoswitch On

PV Name /dev/dsk/c12t3d7
PV Status available
Total PE 3199
Free PE 0
Autoswitch On

PV Name /dev/dsk/c12t6d1
PV Status available
Total PE 3199
Free PE 0
Autoswitch On

PV Name /dev/dsk/c12t6d2
PV Status available
Total PE 3199
Free PE 0
Autoswitch On

PV Name /dev/dsk/c12t6d3
PV Status available
Total PE 3199
Free PE 0
Autoswitch On

[Torsten.]

You alread have 15 (!) PVs:

Max PV 16
Cur PV 15

Are they striped? Check lvdisplay!

Consider to extend the vdisks (if running 11.23 or 11.31).

[Ninad_1]

As per the output you already have 15 disks out of the possible maximum of 16 disks (Max PV) for your VG, also as I had mentioned due to highest disk being 25 GB, you have Max PE per PV = 3199 which anyway wont allow you using more than 25 Gb of disk space whatever size disk you add later.
So the best bet would be to create a new VG - take care this time to have higher Max PV, higher Max PE per PV and also higher PE size [ because with youe PE size you could have gone with max of 512 GB volume size ]
Check man of vgcreate for the options for the above

So create a new VG and then copy the data after creating relevant logical volumes.

Regards,
Ninad

[Sandman!]

As noted your best bet would be to expand the LUN on the storage side instead of extend the VG by adding another PV to it. More because you can add atmost another PV no more than 25GB in size.

~cheers

[Torsten.]

As mentioned before, you can extend the vdisks on EVA to get more space.

If you are running 11.23 or 11.31 you can use "vgmodify" to adjust LVM to use the space. This comes per patch to 11.23.

If you have 11.11, you can still extend the vdisks, but you must backup your data and rebuild the VG on *all* "new" disks.

[Court Campbell]

Maybe I am not thinking correctly, but it seems to me that even if Pete expands the volumes he is still going to hit the Max PE per PV limit. Wouldn't that still leave him pretty much where he is already at.

[Court Campbell]

I want clarify that I mean expanding the LUNs on the eva.

[Torsten.]

Max PE per PV is only 3199.

It can be increased to the real max.

(vgmodify)

[Court Campbell]

Torsten,

I see where you are going. I have not used nor had a chance to use the vgmodify command. I read up on it and now see the option to increase the number of extents per PV -- very nice.

[Torsten.]

According to the docs this should be

/usr/sbin/vgmodify -e max_pe vg_name

see
http://docs.hp.com/en/B2355-60130/vgmodify.1M.html

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

There was also a thread about this these days, but I can't find it at the moment.

[Dave Hutton]

Heres the thread to which patches need to be there:
http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=1139008

Duncan posted it:
You need the following patches:

PHCO_35524
PHKL_36244

[Torsten.]

This is the thread I'm looking for, thank you.

[Sandman!]

BTW what is your OS version 11i or 11.31? As the procedure to use would heavily depend on that. Not to mention that striping and mirroring also play a major role in it.

If you have 11.31 then you can either expand the LUNs on the storage side or modify the VG to upp the Max PV value. This followed by running vgmodify to either make the current PVs visibly bigger to the host or vgextend'ing the VG by the number of LUNs added. Same holds for 11.23 but after all the relevant patches have been applied. For 11.11 and below you can add only one PV or rebuild the VG from scratch - backup the current VG; create a new VG with the desired config and import the data into it.