If you have a Flash-based local storage like SSD disks on your ESXi hosts, It's a recommended operation to use them as the virtual machine's swap file location. So Read Operations of that VMs can be executed very efficient.
Even you use a Disaster Recovery solution like SRM, you can deselect that flash-based datastores (that are provided for swap file) from list of Replicated objects in the vSphere environment.
Backup performance can be better if you want to create a backup when the VM is started and running because in the first state of backup generation, the backup system creates a snapshot from that VM and if the VM's swap file is stored in a SSD datastore, then because of higher read operation rate of SSD disks, time of snapshot creation can be fewer than usual.
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