topic Re: Swap using non-lvm type disk in Operating System - HP-UX

Swap using non-lvm type disk

Smucker — Thu, 17 Apr 2008 18:28:46 GMT

Reading the man page for swapon talks about using any block type device for swap. Leading me to think that a whole disk (san disk) could be used for swap instead of using a standard lvm disk.

I therefore masked/mapped an 8gb disk to the server in need of swap and swapped-on the disk using the block device and it took it.

My question is simple - using swap space in whole disks rather than LVM disk should give better performance due to the LVM layer being removed ... True?

What do the experts think?

Re: Swap using non-lvm type disk

Torsten. — Thu, 17 Apr 2008 18:47:59 GMT

I don't think so, because LVM does not add noticeable overhead.

this idea came from your linux experiences, right?

Re: Swap using non-lvm type disk

melvyn burnard — Thu, 17 Apr 2008 19:29:25 GMT

I disagree. When you define a device for swap you use the CHARACTER device, to remove any overhead that may be induced by using the block device.
The onlyu time swap will really impose any great overhead is if you were to use file system swap, and that can REALLY give a performance hit.

Also, the LVM overhead is so small in reality it would also make little difference

Just my experience

Re: Swap using non-lvm type disk

Tim Nelson — Thu, 17 Apr 2008 20:04:26 GMT

My answer is around the same as Mels.

Once you start swapping/deactivating processes the system performance is so bad that who cares. Having a little faster disk access is miniscule in regards to the performance hit of swapping in the first place.

Never swap...never have time spent worrying about it.