English
Menu

System Architecture and Reliability

In a system, each user request is processed in order by a web server tier, an application server tier and a database server tier. Each request passes through each of the three tiers once, and the maximum number of requests each tier can process is 1,200 per second for the web server tier, 1,000 per second for the application server tier and 900 per second for the database server tier. If the database server tier is upgraded to process 1,500 per second, which is the maximum number of requests the whole system can process?

  1. A1,000 per second
  2. B1,200 per second
  3. C1,500 per second
Show answer and explanation

Answer: A. 1,000 per second

In a system where requests pass through all tiers in order, the number the whole system can process is set by the tier with the lowest capacity (the bottleneck). Before the upgrade, it was set by the database server tier at 900 per second. With the database server tier at 1,500 per second, min(1,200, 1,000, 1,500) = 1,000, so the application server tier becomes the next bottleneck and the whole system stays at 1,000 per second. Removing one bottleneck lets the next-smallest capacity limit the whole system, so performance improvement must look at the entire flow.

  • A. Correct. The application server tier's 1,000 per second becomes the new bottleneck.
  • B. This overlooks the application server tier's capacity and takes the web server tier's capacity as the overall value.
  • C. This is the capacity of the upgraded database server tier. The system cannot process more than the other tiers allow.
Practice this topic Back to topic

Related calculators

RAID Capacity CalculatorCalculate usable capacity, capacity efficiency, how many disk failures can be tolerated and the chance of data loss for RAID 0, 1, 5, 6 and 10 from the number and size of disksAvailability CalculatorCompute availability from MTBF and MTTR, and the availability and annual downtime of systems built from series, parallel and k-out-of-n units

Books on System Architecture and Reliability Ad

As an Amazon Associate I earn from qualifying purchases.

More System Architecture and Reliability questions

  1. Which describes a dual system?
  2. The servers of a semiconductor fab's manufacturing execution system (MES) are made a duplex system consisting of a primary (active) system and a standby system. Which is a characteristic when the standby system is a hot standby?
  3. A system has two redundant load balancers, three web servers behind them, and a single database server used by all the web servers. Among the devices listed here, which is a single point of failure (a point whose stopping stops the whole system)?
  4. A cluster in an active-active configuration shares processing evenly among five servers. Utilization is proportional to the amount of processing. The goal is to keep each server's utilization at 80% or less even when one server fails and the remaining four take over its processing evenly. Which is the upper limit of each server's utilization in normal operation (all five running)?
  5. A system uses three servers with an availability of 0.95 each and has the required capacity as long as at least two of them are running. The servers fail independently, and failures of devices other than the servers are ignored. Which is the availability of this system?