topic Re: Changing maxswapchunks, does it need reboot? in Operating System - HP-UX

Changing maxswapchunks, does it need reboot?

Hunan_1 — Mon, 04 Nov 2002 16:21:17 GMT

Hi all,
I would like to know if changing maxswapchunks needs reboot, and what the value means, Is it the maximun disk space that can be allocated to swap?

Any help is really appreciated.

Re: Changing maxswapchunks, does it need reboot?

Jean-Louis Phelix — Mon, 04 Nov 2002 16:29:03 GMT

Hi,

Yes you have to reboot to change it because it's a static parameter. You probably got this message when trying to add swap space. My advise would be to set it high (> 10000) ...

Total swap space is defined by swchunk * maxswapchunks * DEV_BSIZE(1024)

Regards,

Jean-Louis.

Re: Changing maxswapchunks, does it need reboot?

S.K. Chan — Mon, 04 Nov 2002 16:30:11 GMT

Yes you need a reboot. That value determines or control the maximumum amount of swap you can allocate. The default value of maxswapchunks is 256 and the maximum swap space you can configure is calculated by :-
maxswapchunks*swchunk*1024bytes
The parameter swchunk defaults to 2048. So for example if you leave maxswapchunks to the default 256, the maximum amount of swap you can configure is :-
256 * 2048 * 1024bytes = 512MB

Re: Changing maxswapchunks, does it need reboot?

Patrick Wallek — Mon, 04 Nov 2002 16:31:36 GMT

Yes, changing this kernel parameter does require a reboot.

Maxswapchunks does control the amount of disk space that can be used for swap.

The value is calculated as

maxswapchunks x swchunk x DEV_BSIZE

The values of swchunk (2048) and DEV_BSIZE (1024) should never be changed.

More information on maxswapchunks is available here: http://docs.hp.com/hpux/onlinedocs/939/KCParms/KCparam.MaxSwapChunks.html

Re: Changing maxswapchunks, does it need reboot?

Pete Randall — Mon, 04 Nov 2002 16:33:09 GMT

Yes, changing maxswapchuncks is going to require building a new kernel, and therefore a reboot. From SAM's help on configurable paramters:
"maxswapchunks specifies the maximum amount of configurable swap space on the system"

Pete

Re: Changing maxswapchunks, does it need reboot?

Hunan_1 — Mon, 04 Nov 2002 17:35:46 GMT

Does it need reboot if I add a new device swap for HP-UX 11.00

Re: Changing maxswapchunks, does it need reboot?

Kellogg Unix Team — Mon, 04 Nov 2002 17:49:35 GMT

If you are just adding the swap, you need not reboot the server. That can be done online.
(man swapon)

...Manjeet

Re: Changing maxswapchunks, does it need reboot?

Patrick Wallek — Mon, 04 Nov 2002 17:51:53 GMT

Adding a swap device does NOT require a reboot, assuming maxswapchunks is already large enough for the extra swap space.

If you every want to REMOVE a swap device, this does require a reboot, as swap can not be removed while it is in use.

Re: Changing maxswapchunks, does it need reboot?

steven Burgess_2 — Mon, 04 Nov 2002 17:53:29 GMT

Hunan

Nope,

lvcreate /dev/vg0#
lvextend -L /dev/vg0# /dev/dsk/c#t#d#

The above will ensure file system is allocated to specific disk

swapon /dev/vg0#/lvol#

Then add the swap entry to fstab

/dev/vg0#/lvol# . swap defaults 0 0

HTH

Steve