The PDF I blogged about yesterday included info about 3.0.x and 3.5 features. One of the things that was missing was the option to have the swapfiles created locally. In 3.0.x this done by setting the option “sched.swap.dir” in the .vmx file. The only problem is that this prohibits you from using VMotion for these VM’s. In 3.5 VMware resolved this issue. It’s now possible to set the swap file location to local storage and keep VMotion at the same time. This can be done very easily the following way:
- Edit setting on cluster, click “Swapfile location” and select “Store the swapfile in the datastore specified by the host”
- Click on the ESX Host, click on the “Configuration” tab, click on “Virtual Machine Swapfile Location” and “edit”
Select “Store the swapfile in a swapfile datastore selected below”
Select the local attached storage: [hostname:storage1]
vSphere 4.0 Quick Start Guide
I have seen this option, but have wondered, what the benefits were ?
Du you have any links to performance comparisons, or am i missing another benefit, of doing this ?
The benefits are the fact that you’re not using expensive SAN storage for swapfiles you hardly use anyway. Especially for iSCSI this can be beneficial when the swapfile is used, every single packet that goes to the iSCSI SAN has an overhead because of translations, I would want to limit that as much as possible.
Performance wise I don’t know if it really matters…
any clue where the swap file of the ESX host is located ?
Do you mean the VM swap files or… ?
The ESX host usually stores it’s swap file on the local drive in a partition formatted as swap by the linux OS. So as long as you didn’t change any of the default settings and you have local host storage, that’s where it should be. You should be able to go to a console on the host and type fdisk /dev/sda? and then type p to print your partition table to the screen. That will show you all of your partitions.
[...] Avoid virtual machine swapping to NFS volumes. Edit virtual machine config file to add sched.swap.dir place swap on local storage (supported inline with VMotion in ESX 3.5) [...]