topic Re: Split VG and move to new disks in Operating System - HP-UX

Split VG and move to new disks

Debbie Beresford — Wed, 21 Mar 2012 13:32:54 GMT

I am working on an RP2470 running HP-UX 11.23. We currently have one vg with 9 lvols. We will be replacing our existing disks with larger ones (external SAN). For performance purposes, I am being asked to move each of 4 lvols to separate disks. What is the best way to do this. Mirroring to the new disk was originally suggested but it doesn't seem to make sense if I am going to have to create 5 separate vgs instead of the one large vg.

Re: Split VG and move to new disks

Torsten. — Wed, 21 Mar 2012 13:49:45 GMT

You can have 4 LVOLS on 4 separate disks even if all the disks are within the same VG.

Do you really want to use 4 separate VGs?

Then you can only "copy" (backup/restore) your data from one VG to another.

Re: Split VG and move to new disks

Debbie Beresford — Wed, 21 Mar 2012 14:11:45 GMT

No, I don't necessarily need 4 vgs. I thought if I wanted to make sure the data was on a separate disk I had to do it that way. The disks will be presented from the SAN as 5 separate disks. How do I ensure the lvols go to separate disks? These are for use with an Oracle database. they want data in one place and the database divided into 4.

Re: Split VG and move to new disks

Torsten. — Wed, 21 Mar 2012 14:25:15 GMT

You simply create an lvol with zero size, then use lvextend to extend the LVOL to a specific disk.

Same can be done while mirroring the data, let's say

# lvextend -m 1 /dev/vg01/lvol1 /dev/disk/disk1

# lvextend -m 1 /dev/vg01/lvol2 /dev/disk/disk2

etc ...

Re: Split VG and move to new disks

Debbie Beresford — Wed, 21 Mar 2012 14:31:59 GMT

That sounds great! Kind of like killing 2 birds with one stone! And no data restore. Thanks very much for your help.

Re: Split VG and move to new disks

Torsten. — Wed, 21 Mar 2012 14:36:33 GMT

In case your new LUNs from SAN will be larger than the existing disks you may have a problem with the VG limits (max_pe_per_pv).

In this case you need to increase these values using "vgmodify" first. Then you can mirror your data to the new array LUN.

Re: Split VG and move to new disks

Debbie Beresford — Wed, 21 Mar 2012 14:47:32 GMT

max_pe_per_pv is currently set to 65535. I have one disk presented with a size of 817 GB. I will be presenting 5 disks that will total 1.3 GB. What to I need to change this value to?

Re: Split VG and move to new disks

Torsten. — Wed, 21 Mar 2012 15:11:05 GMT

Please show the output of

# vgdisplay -v vg__

Re: Split VG and move to new disks

Debbie Beresford — Wed, 21 Mar 2012 15:12:58 GMT

sochp3.socan.ca(sudo)> /usr/sbin/vgdisplay -v /dev/vg01
--- Volume groups ---
VG Name                     /dev/vg01
VG Write Access             read/write
VG Status                   available
Max LV                      255
Cur LV                      9
Open LV                     9
Max PV                      16
Cur PV                      1
Act PV                      1
Max PE per PV               65535
VGDA                        2
PE Size (Mbytes)            16
Total PE                    52306
Alloc PE                    42690
Free PE                     9616
Total PVG                   0
Total Spare PVs             0
Total Spare PVs in use      0

   --- Logical volumes ---
   LV Name                     /dev/vg01/u09
   LV Status                   available/syncd
   LV Size (Mbytes)            170000
   Current LE                  10625
   Allocated PE                10625
   Used PV                     1

   LV Name                     /dev/vg01/u08
   LV Status                   available/syncd
   LV Size (Mbytes)            170000
   Current LE                  10625
   Allocated PE                10625
   Used PV                     1

   LV Name                     /dev/vg01/u07
   LV Status                   available/syncd
   LV Size (Mbytes)            40960
   Current LE                  2560
   Allocated PE                2560
   Used PV                     1

   LV Name                     /dev/vg01/u06
   LV Status                   available/syncd
   LV Size (Mbytes)            51200
   Current LE                  3200
   Allocated PE                3200
   Used PV                     1

   LV Name                     /dev/vg01/u05
   LV Status                   available/syncd
   LV Size (Mbytes)            56320
   Current LE                  3520
   Allocated PE                3520
   Used PV                     1

   LV Name                     /dev/vg01/u04
   LV Status                   available/syncd
   LV Size (Mbytes)            56320
   Current LE                  3520
   Allocated PE                3520
   Used PV                     1

   LV Name                     /dev/vg01/u03
   LV Status                   available/syncd
   LV Size (Mbytes)            56320
   Current LE                  3520
   Allocated PE                3520
   Used PV                     1

   LV Name                     /dev/vg01/uw03
   LV Status                   available/syncd
   LV Size (Mbytes)            40960
   Current LE                  2560
   Allocated PE                2560
   Used PV                     1

   LV Name                     /dev/vg01/uw02
   LV Status                   available/syncd
   LV Size (Mbytes)            40960
   Current LE                  2560
   Allocated PE                2560
   Used PV                     1

   --- Physical volumes ---
   PV Name                     /dev/dsk/c18t0d0
   PV Name                     /dev/dsk/c14t0d0 Alternate Link
   PV Status                   available
   Total PE                    52306
   Free PE                     9616
   Autoswitch                  On
   Proactive Polling           On

Re: Split VG and move to new disks

Torsten. — Wed, 21 Mar 2012 15:29:11 GMT

Largest possible LUN size is

Max PE per PV 65535
*
PE Size (Mbytes) 16
=
1048560MB

For a lrager LUN you need to set up a new LUN with a larger PE size.

Re: Split VG and move to new disks

Debbie Beresford — Wed, 21 Mar 2012 16:03:07 GMT

Sorry for the delay in replying. In order to do this would I use the following commands:

vgchange -a n /dev/vg01

vgmodify -e 25 /dev/vg01

vgchange -a y /dev/vg01

Max PE per PV 65535
*
PE Size (Mbytes) 25

= 1638375

Re: Split VG and move to new disks

Torsten. — Wed, 21 Mar 2012 17:13:31 GMT

-e changes the MAX PE PER PV, you cannot change the PE size, sorry.

Re: Split VG and move to new disks

Debbie Beresford — Wed, 21 Mar 2012 17:42:03 GMT

Then how would this be done? Is this something that would be handled on the SAN side?

Re: Split VG and move to new disks

Torsten. — Wed, 21 Mar 2012 18:07:31 GMT

The PE SIZE of a VG is define during the VG creation only.

Re: Split VG and move to new disks

Debbie Beresford — Wed, 21 Mar 2012 18:24:42 GMT

So if I create a new VG with the larger size, can I still mirror to get the data over? If not , am I back to doing a restore?

Re: Split VG and move to new disks

Patrick Wallek — Wed, 21 Mar 2012 18:34:35 GMT

Let's step back a minute. I think we are getting confused.

You current VG parameters allow for a SINGLE disk of 1 TB in size.

PE SIZE = 16 MB

MAX PE PER PV = 65535

16 MB x 65535 = 1,048,560 MB = 1,023 GB = 0.999 TB

If the disks you are adding are SMALLER than 1 TB you should be OK. I believe you said that the TOTAL size of the disks you are adding is 1.3 TB, correct? BUT no SINGLE disk is larger than 1 TB is it?

Re: Split VG and move to new disks

Torsten. — Wed, 21 Mar 2012 18:38:43 GMT

How large the LVOLs should be?

If you create a new VG, you cannot mirror your data.

But if the size of a PV is limited to 1TB, you can create as much PVs as possible for your VG (max is currently 16 disks per VG in your setup - this gives you a VG of 16TB).

Re: Split VG and move to new disks

Debbie Beresford — Wed, 21 Mar 2012 18:46:09 GMT

Patrick, you are correct. I would be adding 1 disk that is 600 GB and 3 that are 300 GB. That adds up to a bit more than I said but there is some extra space. If what you are saying is correct, I should be fine.