Split VG and move to new disks

[Debbie Beresford]

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.

[Torsten.]

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.

[Debbie Beresford]

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.

[Torsten. · Accepted solution]

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 ...

[Debbie Beresford]

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

[Torsten.]

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.

[Debbie Beresford]

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?

[Torsten.]

Please show the output of

# vgdisplay -v vg__

[Debbie Beresford]

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
 

[Torsten.]

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.