vm reservation swap file

[tdubb123]

when should i be setting a reservation for a vm? why is it that when i set the reservation, there is no swap file?

[mcowger]

let me answer in reverse order:

1) Why is there no swap file?  Because when you set a 100% reservation on the VM, you are guarenteeing that physical memory will always be available for the virtual machine, and therefore there is 0 chance it will ever get swapped out.  Hence, no need for a vswp.

2)  You would set a reservation when you need to absolutely guarentee that even if your host is overcommited on memory that this VM (probably an important one) will never suffer reduced performance by being swapped out in favor of other VMs.

[depping]

Keep in mind that when you set a reservation it could potentially skew the HA slotsize depending on which admission control policy you use. For more details check my deepdive HA blog.

[rsicilia]

The RAM reservation grant to your VM access to phisical RAM. If the RAM is reserved the swap file is aimless because the VM uses only phisical RAM.