“DB File Sequential Read” Wait Event

In a previous post, I have discussed steps and methods to calculate I/O wait from an Oracle AWR report. The key and sometimes challenging task is to identify a wait event which is related to the storage. While many waits may be caused by I/O related performance issues, the following waits are the main ones…

Active-Active vs. Active-Passive Storage Controllers: Why Should You Even Care?

If you don’t have a great understanding of storage controller design, you are in excellent company. In fact, many IT veterans have only a basic understanding of the different controller architectures out there. And most everyone’s eyes start to glaze over when the terms active-active and active-passive controllers start getting thrown around. And if you made…

Measuring I/O Wait – Part 1: Oracle

Storage performance 101 starts with three measurements: IOPS, latency and throughput. While these measurements are important, they are secondary to the I/O wait measurement. The IOPS, latency and throughput should be measured and analyzed only after you have a clear picture of the I/O wait time. Several weeks ago, I discussed the concept of I/O…

What Is “I/O Wait”?

The concept of I/O wait is very important, and, unfortunately, many application owners and DBAs do not completely understand what it is or how to measure it. This is probably the most important concept to understand when evaluating the I/O performance of your storage. Since I/O wait will be mentioned in many future topics, I’ll…

What Is an Acceptable I/O Latency?

When discussing storage performance of many RDBMS applications, I/O latency is one of the most important topics. Today, I would like to discuss my view on latency monitoring. In a future post, I will be talking about latency, throughput, and IOPS, and in which situation each is most important. I/O latency is defined simply as the…