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.

5 comments:

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

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

    How you determine value of seconds?

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

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

    Could you please provide the reference technet article link?

    ReplyDelete
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