One of the things that I often hear from large companies is that they spend time testing systems, burning them in, and looking at the ways different configurations might affect their applications. However in so many of the companies I've worked for, we haven't the extra hardware or luxury of time to test different configurations, or even alter our configuration once we have hardware. It seems to fall to the DBA to "guess" right from the start about the specifications needed for new servers.
That got me thinking about something that would be handy for examining hardware. What if a tool could take the workload of a server, looking at the volume of queries, and then determining the rate, ratio, and types of I/Os that the application performs. Rather than look at the queries, look at the work that the queries do.
I could then take that workload and have it replay that workload, that volume of disk I/O, and even memory accesses, against another system. Perhaps I could even have it scale up to a multiple of the original workload. Perhaps taking 100 disk reads/sec and applying 1,000 disk reads/sec. If it ran on a system, it could stress the system like SQLIO, allowing you to get an idea of what your hardware will do as the application scales.
It's something that I think would allow us to make a better guess about what level of hardware to order, and it might even allow a developer to see just how poorly their queries perform at scale. They don't need to generate large amount of data, or pay for a tool to simulate lots of clients. They could use this tool instead to simulate more work being done. It might even be something you could show to managers as evidence of why you need to spend more time testing and tuning your code.
Steve Jones
The Voice of the DBA Podcasts
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