Tag Archives: use disk as swap

Adding extra or secondary swap in HPUX

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Learn how to add a secondary swap or extra swap in running the HPUX system without any downtime. It uses free space in root VG to mount as swap.

When the system runs low on memory and swap continuously, its time to troubleshoot. Even after troubleshooting and all available app/OS tuning you are still running out of memory then you can try adding extra swap before you think of adding RAM to the server which involves cost/resources of parent machine.

Step 1

For adding extra swap check how much space you have available in root volume group vg00. Use vgdisplay command to get free PE and PE size numbers.

# /usr/sbin/vgdisplay vg00
--- Volume groups ---
VG Name                     /dev/vg00
VG Write Access             read/write
VG Status                   available
Max LV                      255
Cur LV                      9
Open LV                     9
Max PV                      16
Cur PV                      2
Act PV                      2
Max PE per PV               4384
VGDA                        4
PE Size (Mbytes)            16
Total PE                    6544
Alloc PE                    5978
Free PE                     566
Total PVG                   0
Total Spare PVs             0
Total Spare PVs in use      0

Here we have 566 free PE with 16MB size of each. This sums up to 8.8GB of free space in root VG. We can use space from this 8.8GB for adding extra swap.

Read our Linux swap related articles :

Check the current swap configuration. Here you can see like default HPUX configuration, lvol2 is mounted as swap.

# /usr/sbin/swapinfo -tam
             Mb      Mb      Mb   PCT  START/      Mb
TYPE      AVAIL    USED    FREE  USED   LIMIT RESERVE  PRI  NAME
dev       43008       0   43008    0%       0       -    1  /dev/vg00/lvol2
reserve       -    1963   -1963
memory    40861    9261   31600   23%
total     83869   11224   72645   13%       -       0    -

Step 2

Create a new contiguous logical volume with no bad block relocation policy and size of your requirement. Let’s make an LV of 2GB. 

# lvcreate -L 2048 -C y -r n /dev/vg00
Logical volume "/dev/vg00/lvol10" has been successfully created with character device "/dev/vg00/rlvol10"
Volume Group configuration for /dev/vg00 has been saved in /etc/lvmconf/vg00.conf

Step 3

Start swap on this lvol. Add -f argument to start forcefully if the below command fails. 

# swapon -p 1 /dev/vg00/lvol10

Step 4

Edit /etc/fstab to mount this LV as swap on every boot. Add below entry : 

/dev/vg00/lvol10 ... swap pri=1 0 1

Step 5

Check again swap size. Now you can see new lvol is added in the swap.

# /usr/sbin/swapinfo -tam
             Mb      Mb      Mb   PCT  START/      Mb
TYPE      AVAIL    USED    FREE  USED   LIMIT RESERVE  PRI  NAME
dev       43008       0   43008    0%       0       -    1  /dev/vg00/lvol2
dev        2048       0    2048    0%       0       -    2  /dev/vg00/lvol10    
reserve       -    1963   -1963
memory    40861    9261   31600   23%
total     85917   11224   74693   13%       -       0    -