Some notation
Wednesday, February 10, 2010
10:18 AM
Some notation: 
P = performance = time spent between request and response. 
Pminimum = minimum theoretical response time.
PSLA = SLA upper bound on response time. 
We want Pminimum ≤ P ≤ PSLA
But remembering our notation from last time: 
tserver = time spent in server to be scaled.
tnetwork = time spent in network communications.
tcloud = time spent waiting for cloud.
tminimum = theoretical minimum server time. 
tSLA = maximum time that can be spent on server to comply with SLA.
We want Pminimum = tminimum+tnetwork+tcloud 
≤ P = tserver + tnetwork + tcloud 
≤ PSLA = tSLA + tnetwork + tcloud  
Pminimum ≤ P ≤ PSLA whenever tminimum ≤ tserver ≤ tSLA. 
(Here, and from now on, tcloud includes cloud communication time and tnetwork is just from client to edge and back.)