SLOB2: Essential for Every DBA Toolkit

slob ghostA couple of weeks ago, Kevin released the second version of SLOB – the Silly Little Oracle Benchmark. Readers will know that I was already a big fan of the original version, but version 2 (which I was fortunate enough to test prior to its release) now has extra features and functionality which make it the definitive load generation tool for Oracle databases. To put it simply, every DBA should now have SLOB2 in their toolkit.

Why? Well, SLOB allows you to learn things. It allows you to study performance and test the effect of changes that you introduce to a stable system. It allows you to find bottlenecks. And most importantly for me, it allows you to write test harnesses which build up a picture of the complete performance characteristics of a system.

Here’s an example using my two-socket eight-core Sandy Bridge-EN server. What’s the maximum number of IOPS I can drive through an Oracle database when running a read-only workload? What about a workload with 10% writes, or 20% or 30%? And what latencies does the storage deliver? Using SLOB2 with my PIO test harness (located here) I can easily generate all of these results and plot them on a graph:


Each line on the graph represents a SLOB test with a specific UPDATE_PCT value (0%, 10%, 20% or 30%). The line plots the IOPS vs Latency results as the number of SLOB worker processes ramps up from 1 to 64. You can see that, as you might expect, each line reaches a peak value of IOPS which the system can deliver (limited in this case by the server, not the storage) then starts to fall back down. From this graph you can fairly easily predict the behaviour as the UPDATE_PCT values increase further. Sometimes a picture really is worth a thousand words.

I’ll be posting some more SLOB test results and ideas soon. For now, my recommendation is to download it and use it. SLOB isn’t just a benchmark tool, it’s a learning tool. Use it wisely and you will come to understand a lot more about Oracle performance.


2 Responses to SLOB2: Essential for Every DBA Toolkit

  1. kevinclosson says:

    > What about a workload with 10% writes, or 20% or 30%?

    Nice post. Regarding the bit about writes, however, it might be better to say 10,20,30 percent “modify DML”. If you use ~misc/ you’ll probably find that the modify DML percent doesn’t map to a physical I/O read-write split.

    • flashdba says:

      Hey Kevin

      You’re right – the way I phrased that made it confusing. The UPDATE_PCT parameter affects what goes in, not what comes out.

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