For best performance, use on disks local to the ESXi Host, Storage Area Network (SAN) storage devices, or Network File System (NFS) shares. Network storage system performance (IOPS and latency) must not impact the ability of the virtual machine to perform I/O operations in a timely fashion. CPU I/O wait times of the virtual machine should be zero or very close to zero. Slow network I/O performance can cause serious stability issues with the OS and the application.