1 © Copyright IBM Corporation /2013 The Sizer Advisor - v1.0 The Sizer Advisor Ten Elementary Advices Every Sizer Should Follow v1.0 Jorge L. Navarro The Sizer Advisor Ten Elementary Advices Every Sizer Should Follow v1.0 Jorge L. Navarro Demystifying Response Time Series

2 © Copyright IBM Corporation /2013The Sizer Advisor - v1.0 Why The Sizer Advisor? The Expert SizerThe Novice SizerThe Author I'd love someone has taught this to me when I began working in sizing Here are ten pieces of advice I should know and follow It would be better a live presentation, but this is a starting point...

3 © Copyright IBM Corporation /2013The Sizer Advisor - v1.0 Contents 1. Understand the performance metrics. 2. Know the most used performance benchmarks. 3. Don't get obfuscated by benchmarketing. 4. Variability is your worst enemy. 5. Size the true peak load. 6. Avoid the "what is the peak" pitfall. 7. Be aware of the consequences of undersizing. 8. Design a balanced system. 9. Garbage In, Garbage Out. 10. Master the sizing tool.

4 © Copyright IBM Corporation /2013The Sizer Advisor - v1.0 Customer: a passenger. Customer: a passenger. Service (or Unit Of Work): transport from Llavaneres to Barcelona. Service (or Unit Of Work): transport from Llavaneres to Barcelona. Definitions 0 0 Example #1: Bus Transport Arrival Departure Queue/Waiting roomServer(s) In Queue In Service Customers willing to receive serviceCustomers after receiving service Service Center Customer: a citizen. Customer: a citizen. Service (or Unit Of Work): a request to the public administration. Service (or Unit Of Work): a request to the public administration. Example #2: Public Desk Customer: a user. Customer: a user. Service (or Unit Of Work): a certain information system transaction. Service (or Unit Of Work): a certain information system transaction. Example #3: Server

5 © Copyright IBM Corporation /2013The Sizer Advisor - v1.0 Understand the Performance Metrics 1 1 Actual number of services (units of work) performed per unit time. Unit: UOW/time. Throughput (X) The maximum throughput the service center can deliver. Unit: UOW/time. Bandwidth (B) 50 available seats. 50 available seats. 25 occupied seats. 25 occupied seats. Throughput = 25 passengers/hour. Throughput = 25 passengers/hour. Bandwidth = 50 passengers/hour. Bandwidth = 50 passengers/hour. Usage = 50%. Usage = 50%. Service Time = 1 hour. Service Time = 1 hour. Response Time = 1 hour (nobody have to wait for next bus because current is full). Response Time = 1 hour (nobody have to wait for next bus because current is full). Performance Metrics The time elapsed from the beginning to the end of a service. Unit: time. Service Time (S) The total time spent at the service center, sum of the service time and the wait time. Unit: time. Response Time (R) The time elapsed waiting to be serviced. Unit: time. Wait Time (W)

6 © Copyright IBM Corporation /2013The Sizer Advisor - v1.0 Know the Main Performance Benchmarks SAPSIOPSTPMName SAP Application Performance Standard. SPC-1 Input/Output operations per second. TPC-C (OLTP) transactions per minute (tpmC). OwnerOrganization SAP AG (sap.com/benchmark) Storage Performance Council (storageperformance.org) Transaction Processing Performance Council (tpc.org) Service Center An information system running SAP A Storage Device An OLTP information system running a RDBMS. Unit TypeThroughput (with response time limit) Bandwidth (response time must be informed) Throughput (with response time limit) UOW Process line items in a sales order. Read/write requests to the storage device. OLTP transactions against a relational database. Definition 20 fully processed order line items per hour. 60 dialog steps (screen changes) per hour. 24 SAP transactions per hour. Maximum I/O requests per second (at the 100% load point). Database transactions per minute. 2 2

7 © Copyright IBM Corporation /2013The Sizer Advisor - v1.0 Don't Get Obfuscated by Benchmarketing 3 3 Maximum Velocity = 250 Km/h Benchmark UOW = 100 Km drive from A to B. UOW = 100 Km drive from A to B. Service Time = aprox 24 mins. Service Time = aprox 24 mins. Expected Performance System Under Test Warning: Good published benchmark performance is a necessary but not a suficient condition to get real world performance. Warning: Good published benchmark performance is a necessary but not a suficient condition to get real world performance. A Typical Disclaimer:...SAP standard benchmarks and productive customer implementations VARY SIGNIFICANTLY from each other and, therefore, any statement of GUARANTEE may be potentially damaging. A Typical Disclaimer:...SAP standard benchmarks and productive customer implementations VARY SIGNIFICANTLY from each other and, therefore, any statement of GUARANTEE may be potentially damaging. Service Time = 1,5 hour. Service Time = 1,5 hour. Actual Performance The Real World Average Velocity = 60 Km/h Real World

8 © Copyright IBM Corporation /2013The Sizer Advisor - v1.0 Variability is Your Worst Enemy 4 4 Scenario: A Public Service DeskPerfectlyRegular Not So Regular Real World RandomnessArrivals Regular, scheduled. I.e. 9:00, 9:15, 9:30... Scheduled. Clustered in pairs. I.e. 9:00, 9:30, 10:00... Random. Unpredictable. Service Time Constant I.e.: 15 min. Constant Random. Unpredictable. KPI Customers never have to wait. System at 100% usage. One of the two doesn't wait and the other must wait 15 mins. System at 100% Usage. Waits. System at less than 100% usage. Sometimes busy, sometimes idle. Remedy Not needed (there is no problem). A second desk. Oversizing (extra additional capacity). How much? Until waits are "reasonable", typically at 65% usage. KPI after remedy No waits. The two are serviced simultaneously. 50% usage. There are waits, but at an acceptable level. The variability, both in customer arrivals and in service time, is the main reason for oversizing servers.

9 © Copyright IBM Corporation /2013The Sizer Advisor - v1.0 Size the True Peak Load 5 5 Class A + Class B = Total Peak Peak Peak Peak Peak Peak = = 740 Without Considering Timebase Time Class A Class B Total > = > = 540 Considering Timebase The maximum concurrent or simultaneous load (540). The maximum concurrent or simultaneous load (540). The knowledge of the load time evolution is highly recommended to prevent this excess evaluation (740 instead of 540). The knowledge of the load time evolution is highly recommended to prevent this excess evaluation (740 instead of 540). The Peak Load is... Class A Time Interval Class B 20%9-1110% 50% % 30% % 1000 Total Arrivals 300 Two Customer Classes, A and B, accesing the same service center. What is the PEAK load?

10 © Copyright IBM Corporation /2013The Sizer Advisor - v1.0 Avoid the "what is the peak" pitfall 6 6 Averaging time too low. Averaging time too low. Too much detail. Too much detail. Good for performance analysis. Good for performance analysis. Useless for sizing. Useless for sizing. Peak usage is 100% Same data, varying the averaging time... Averaging time right to the point. Averaging time right to the point. The right level of detail. The right level of detail. Good for sizing. Good for sizing. Peak Usage is 70% Averaging time too high (10 hours averege). Averaging time too high (10 hours averege). Total loss of detail. Total loss of detail. Good for trending analysis. Good for trending analysis. Useless for sizing. Useless for sizing. Peak Usage is 50%

11 © Copyright IBM Corporation /2013The Sizer Advisor - v1.0 Be Aware of the Consequences of Undersizing 7 7 Incoming Requestors 60 at peak hour (1 per min) Bandwidth: 30 request per hour. In the best conditions (customers arriving 1 min apart) the customers would have to wait an average of 29,5 min, and a maximum of 59 min! Ravg > 30 min. Rmax = 61 min. Undersized Incoming Requestors 60 at peak hour (1 per min) Bandwidth: 60 (2x30) request per hour. In the best conditions (customers arriving 1 min apart) none of them have to wait. So the average and the maximum response time are 0. Ravg = 0 min. Rmax = 0 min. Rightsized Insane Response Time increase!

12 © Copyright IBM Corporation /2013The Sizer Advisor - v1.0 Design a Balanced System 8 8 Desk A Desk B Looong Queue...Nobody! Incoming Service center bandwidth is 2x, but due to unbalance (customer bias) it runs at 1x. Highly unbalanced. Storage is the bottleneck. Choose the same "size" for every component. Highly unbalanced. Storage is the bottleneck. Choose the same "size" for every component. A SAPS capable server A 1000 IOPS capable storage + = A 2000 SAPS capable system Typically 0,5 IOPS/SAPS

13 © Copyright IBM Corporation /2013The Sizer Advisor - v1.0 T-Shirt size: XS, S, M, L, XL, XXL. T-Shirt size: XS, S, M, L, XL, XXL. Concurrent users and their activity. Concurrent users and their activity. Throughput: transactions and objects. Throughput: transactions and objects. Comparison with similar implementations. Comparison with similar implementations. Custom benchmarks. Custom benchmarks. Garbage In, Garbage Out Each sizing method has its own precision What if analysis. What if analysis. To know how the output depends on the several inputs. Identify the most critical inputs, the ones with higher impact in the output. Sensitivity Analysis is Highly Recommended If input is between X and 2X, output will typically be between Y and 2Y (or broader). If input is between X and 2X, output will typically be between Y and 2Y (or broader). Approx is not equal to 1003! Approx is not equal to 1003! Excess precision in the output (i.e. 2345,6 SAPS) hurts the eyes, and moreover is false. Excess precision in the output (i.e. 2345,6 SAPS) hurts the eyes, and moreover is false. Precision of the sizing output 9 9 (Im)preciseInputs (Im)preciseOutputs Sizing Procedure

14 © Copyright IBM Corporation /2013The Sizer Advisor - v1.0 Master the Sizing Tool 10 Output: SizingInput: Throughput Average or Peak Time Interval Processed during Time Interval Database Residence Time Interval Endpoints Items in an object Sizing Element Input: Active Users (1/12) * Medium Activity 1 interaction step every 30s 3 * Medium Activity

15 © Copyright IBM Corporation /2013 The Sizer Advisor - v1.0 The Sizer Advisor Ten Elementary Advices Every Sizer Should Follow v1.0 Jorge L. Navarro The Sizer Advisor Ten Elementary Advices Every Sizer Should Follow v1.0 Jorge L. Navarro Demystifying Response Time Series