Flash Read Cache This completely new feature in vSphere 5.5 provides a mechanism for utilizing fast SSD as a Linux host swap cache or to provide improved read speed for a host virtual disk. To make use of this feature, you first have to create a new resource, as shown in the screenshot. Then you must connect to that resource from each VM needing access. For a Linux guest, this would consist of configuring a swap disk to use part of the read cache. Another option would be to enable caching for a VM.