VMware vSphere 5.5 Disk Scheduler and the mClock Caveat
As more VMware customers make the jump to vSphere 5.5 as their hypervisor platform, some of the advantages are becoming clear. Storage is one area where there are some significant gains by utilizing vSphere 5.5, and at the same time it is good to understand that there can be caveats as well.
The New vSphere Disk Scheduler
Duncan Epping, who was recently promoted to Chief Technologist, wrote an article which highlights the new disk schedule used in vSphere 5.5. Inside the article you can follow links to the deep dive on mClock which will give you a detailed view of the engine that handles the new I/O scheduler.
Along with understanding the benefits of the new vSphere disk scheduler, Duncan also brought up an interesting note in his follow up article on the mClock caveat which surrounds the use of I/O limits. The article tackles the often misunderstood subject nicely and is a must read for any VMware administrator.