Citrix Machine Creation Services (MCS) is noted to generate 21.5 % more Average IOPS (Inputs and output per second) when running in steady state and compared to Citrix Provisioning Services (PVS)
This breaks down to roughly 8% more Write IOPS and 13% more Read IOPS than PVS.
MCS Creates 45.2% more Peak IOPS when compared to PVS
PVS has a Read/Write ratio of 90%+ Writes when the VM is running in Steady or Peak mode
MCS has a Read/Write ratio of 47/53% during Peak VM operation
MCS has a Read/Write ratio of 17/83% during Steady state
So it's now widely considered that MCS is now a perfectly viable option that can be used as an alternative to PVS. (Depending on the requirements) If the Reads Ratio can be reduced during the VM Stable running state, then this would make the write difference beween MCS and PVS negligable. You have to consider whether the remaining write difference is worth negating for the ease of configuration and management that MCS offfers. Ok, it may not be a solution for all cases, but it's certainly no longer a second thought. There are technologies to reduce the READ ratio during VM stable running status, such as the hypervisor caching technologes used by Hyper-V and VMware.
The diagram below illustrates the Read/Write ratio against IOPS for a Windows VM. This is the lifecycle of a VM from Bootup to running state.
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