Swap location in VM

[Patrick Ambuhl]

Hello,
What would be the best option for the swap of a VM ?
Currently the swap is on the boot disk and I don't like that because this disk is a mirrored SAN LUN and I think that my I/Os should be used for more productive operations than copying the swap datas on a remote site...

I have the following options :
- Create a non replicated LUN and assign it to my VM.
- Use a local (on the host f/s) file and present it as a disk to the VM.

If you have other options, let me know.

Thanks

Patrick

[Torsten.]

This may depends on the client OS (hp-ux, linux, windows ...).


A SAN can even be faster than a local SCSI connection.

[Venkatesh BL · Accepted solution]

> - Use a local (on the host f/s) file and present it as a disk to the VM.

I think you should avoid this. file based swap is very slow and would hit performance a great deal during memory pressure situations.

[Jozef_Novak]

Hello Patrick,

if you don't have a Serviceguard configuration (the VM does not fail over to the remote site), then you're right stating that replication of the VM swap is just a waste of I/O.

Both of your options as you have mentioned them are possible. If you have enough diskspace on your VM host's local disks then use it. Just don't swap into a file, rather use raw disks or logical volumes as backing stores for VM swap.

If you are lacking local disk space or if you have a SAN that clearly outperforms your local SCSI disks, then go for the SAN LUN option. Again, use a raw device or a logical volume as a backing store. From performance standpoint, it is better to avoid the filesystem overhead.

HTH,
J.

[Patrick Ambuhl]

Hello,
Thanks for your fast and clear answers, I'll go with the SAN LUN option because the guy that installed the host did not leave any free space.

Patrick