topic Re: Mirroring Swap in Operating System - HP-UX

Mirroring Swap

benseghir_1 — Sun, 30 Mar 2008 09:19:16 GMT

Hi,

My question, is it necessary to mirror swap volume??

I have 2 internal disks for vg00 and I need more swap and for best performance I want to define 2 volumes not mirrored, each one on one physical disk??

I suppose that the important is that I have 1 swap volume on each disk!!

Is it correct??

Tanks

Re: Mirroring Swap

piyush mathiya — Sun, 30 Mar 2008 09:30:54 GMT

Friend,
It is not important to mirror secondary swap space. but if you will do then it will good. And yes it is really good thought that create swap volume on different different disks.

Regards,
Piyush Mathiya

Re: Mirroring Swap

Torsten. — Sun, 30 Mar 2008 09:37:57 GMT

If your swap is not mirrored and the disk fails, your system will crash. As long as the disk is bad you will not be able to restart your system because you don't have a swap device.

Re: Mirroring Swap

Sajjad Sahir — Sun, 30 Mar 2008 09:41:37 GMT

by keeping mirror copies of root,boot and primary swap logical volumes on another disk, u can use the copies of the to keep u system in operation if any of these logical volume fails.

also device swap has the better perfomance than file system swap.
##I suppose that the important is that I have 1 swap volume on each disk!!
if it is separate disk which is better

Re: Mirroring Swap

Steven E. Protter — Sun, 30 Mar 2008 10:58:19 GMT

Shalom,

Much debated, never resolved.

Some do mirror swap, some do not.

I like a system to be able to run many days with its mirror disk broken, that is impossible without mirroring swap.

Its a matter of opinion though and you will get many answers.

SEP

Re: Mirroring Swap

SKR_1 — Sun, 30 Mar 2008 11:17:58 GMT

Torsten is right.

Re: Mirroring Swap

benseghir_1 — Sun, 30 Mar 2008 11:40:45 GMT

Hi all,

Thanks for your answers, i want just to precise that, I have vg00 with 2 physical disks, I have all OS logical volumes mirrored, also swap volume, but I want to modify the swap volume with 0 mirror copie and create the second swap volume on the second disks, the two swap volumes not mirrored.

I suppose that if my first disk fail, I can boot from the second disk because I have one volume swap on.

Thanks

Re: Mirroring Swap

James R. Ferguson — Sun, 30 Mar 2008 14:40:17 GMT

Hi:

IF you don't mirror your *primary* swap then you run the risk of a system crash or failure to boot as Torsten noted.

Ask yourself why you would lock every door in your house but one.

Mirroring is a high-availabilty strategy and not mirroring primary swap lessens your protection.

When you configure a system, your primary swap can be *less* than your total physical memory (although disk is cheap!). Then, configure a *secondary* swap on a non-vg00 volume or volumes. Ideally, mirror or Raid protect those logical volumes too, but if not, at least you will have made it easier to reboot and/or replace a failed physical disk in vg00.

Regards!

...JRF...

Re: Mirroring Swap

benseghir_1 — Tue, 01 Apr 2008 08:58:30 GMT

Hi all,

It clear for me now, many thanks to all for your help.

Best Regards