Steve Herrod discussed in Wednesday’s Keynote at VMware Partner Exchange: Las Vegas that vSphere will soon have the ability to set DRS Resource Shares on I/O per VM.
As many different workloads hit the same set of disks/arrays/spindles, low priority processes that run “ad-hoc” will cause higher priority systems to experience reduced performance. What you want to see is that the low priority VM gets less performance than the higher priority systems.
The new ability works by assigning out shares based on disk performances. Just like CPU/Memory shares of the original ESX days. Higher shares total for a host gets higher priority for that shared VMFS volume.
The first case study discussed covered two separate hosts with the IO DRS turned on running the same workload levels, and saw a pretty significant difference in terms of IOPS & Latency measures. With it turned off both VMs ran at 20 ms & 1500 IOPS. With it on the Latency changed to 16 ms and 31 ms and a similar spread for IOPS!
After showing the demo the presenters asked if anyone in the packed room would find a value to this? Everyone immediately raised their hands.
