Wednesday, 5 September 2012

How to Calculate the number of WFE server

Here is how you can calculate the number of web front end servers in a SharePoint farm.
 Workload Characteristics Value Keyword Total number of users 30000 Total number of unique users per day 20000 N Concurrency Rate 0.3 C Requests per day per user 400 RPD Peak usage ratio 3 Hours in the business day 24 Average peak RPS 83.33333333 % Low-cost requests 0.25 % Medium-cost requests 0.4 % High-cost requests 0.35 Weighted peak RPS 266.6666667 Number of WFEs needed (@100 RPS/server) 2.666666667

Calculate RPS:
N: Total number of unique users ("20,000 of whom access the farm on any given day")
C: Concurrent user rate ("30 percent of the users will use the portal at the same time")
RPD: Requests per day per user ("Each user makes 400 requests in the course of a business day")
Peak usage ratio = 3 ("peak usage can be as much as three times")
Average RPS = (N * C * RPD * Peak Usage)/seconds
Calculate Weighted RPS based on type of usage
High-cost weight:             5
medium-cost weight:     3
low-cost weight:              1

% Low requests = 25% ("25 percent of requests involve tagging documents and similar activities")
% Medium requests =  40% ("40 percent of requests consist of operations such as accessing information in legacy systems")
% High requests = 35% ("everything else")
Calculate the weighted requests:
Weighted high RPS = (Average RPS* %high-cost requests * weight)
For example, high-cost requests have a weight of 5 = (83.3*0.35*5)
Weighted peak RPS = Weighted high RPS + Weighted medium RPS + Weighted low RPS
Calculate number of WFEs:
Number of WFEs is calculated using weighted peak RPS/100
Reference for this is MOC, technet. This is applicable for SharePoint 2010 and 2013.

1. How did you estimate or calculate the weight?
High-cost weight: 5
medium-cost weight: 3
low-cost weight: 1

2. For calculating
Average RPS = (N * C * RPD * Peak Usage)/seconds

How you determine value of seconds?

1. It's the business day x 3600. 3600 is the seconds per hour.

3. "Reference for this is MOC, technet. This is applicable for SharePoint 2010 and 2013."

4. 5. 