Exchange Server 2010 'Throttling Policies and CPUStartPercent'

Throttling policies have a parameter called “CPUStartPercent” that defines the starting CPU use percentage at which Exchange will begin delaying inbound requests. EWS, Exchange Active Sync, POP and IMAP honor the CPU Start Percent value in Microsoft Exchange Server 2010. “Three things to keep in mind: 1. sampled CPU percent is across all CPUs. So […]

Throttling policies have a parameter called “CPUStartPercent” that defines the starting CPU use percentage at which Exchange will begin delaying inbound requests. EWS, Exchange Active Sync, POP and IMAP honor the CPU Start Percent value in Microsoft Exchange Server 2010. “Three things to keep in mind: 1. sampled CPU percent is across all CPUs. So at a CPUStartPercent of 75%, it would have to be using 75% of ALL CPUs for sleep throttling to kick in. 2. sampling logic is an average over roughly a 10 second rolling window. This keeps us from responding to quick spikes in CPU. 3. This parameter is *per throttling policy*. This means that you could assign a different CPU start percent for Jane than you do for John. This’s particularly useful if you’ve a service account whose work is more important than your ordinary user and where you just don't care if it taxes the system. Make wise decisions about this one, though, as a heavily taxed EWS will affect the user experience for someone using Outlook Web App (for example),” noted David Sterling.