SSDs in servers
A key consideration when contemplating the use of SSDs for Hyper-V hosts is what type of SSD you should use. The answer is to always use enterprise class SSDs, not consumer SSDs, for these kinds of scenarios. In particular you should use SAS (Serial Attached SCSI) SSDs rather than SATA (Serial ATA) SSDs in your hosts for the following reasons:
- Their controller is more powerful
- Their write latency is much smaller
- Their endurance cycle (number of writes before failure) is much longer
- Their reservation (free) space is much larger
- Their garbage collection algorithm as implemented in their firmware is more effective
SSDs may use either single-level cell (SLC) or multi-level cell (MLC) flash technologies, and enterprise SSDs generally use eMLC (enterprise MLC) which enhances MLC with wear-levelling, deduplication, redundancy and write optimization technologies. A good explanation of the differences between these various technologies can be found in the article MLC vs SLC: Which flash SSD is right for you? found at:
SAS SSDs are ideal for hosting operating system volumes as they can increase manageability by making operating systems faster and more responsive. SATA SSDs can still have a place however in your Hyper-V environment, particularly in scenarios where no writes are involved. For example, if you are going to use a parent virtual hard disk (VHD) to create differencing disks, you need to set the parent VHD as read-only to prevent it from being modified. You could therefore opt to use cheaper SATA SSDs for storing such parent VHDs.
The above tip was previously published in an issue of WServerNews, a weekly newsletter from TechGenix that focuses on the administration, management and security of the Windows Server platform in particular and cloud solutions in general. Subscribe to WServerNews today by going to http://www.wservernews.com/subscribe.htm and join almost 100,000 other IT professionals around the world who read our newsletter!
Mitch Tulloch is a twelve-time recipient of the Microsoft Most Valuable Professional (MVP) award and a widely recognized expert on Windows Server and cloud computing technologies. Mitch is also Senior Editor of WServerNews. For more information about him see http://www.mtit.com.