Due to the random I/O nature of any database solution, running MySQL within a virtualized environment places a heavy load on the storage solution you are using. To help keep the performance of your virtualized solution at the highest level, use the following notes to help configure your systems.
Some virtualization solutions permit you to use a physical disk directly within your virtual host as if it were a local disk. Use this whenever possible to ensure that disk contention issues do not affect the performance of your virtual environment.
When running multiple virtual machines, use an individual disk for each virtual instance. Using a single disk and multiple partitions, with each partition dedicated to a virtual host, leads to the same contention issues.
If you are using standard file-based storage for your virtualized disks:
File-based storage is subject to fragmentation on the host disk. To prevent fragmentation, create a fixed-size disk (that is, one where the entire space for the disk file is preallocated) instead of a dynamic disk that grows with usage. Be prepared to defragment the disk hosting the files at regular intervals, to reduce the fragmentation.
Use separate disk files for the operating system and database disks, and try to avoid partitioning a disk file as this increases the contention within the file.
Use a high-performance disk solution, such as RAID or SAN, to store the disk files for your virtualized environments. This improves the performance of what is essentially a large single file on a physical device.
When running a number of different virtualized environments within a single host, do not use the same physical host drive for multiple virtual disks. Instead, spread the virtual disks among multiple physical disks. Even when using a RAID device, be aware that each virtual host is equivalent to increasing the load linearly on the host RAID device.