I’ve done a minor update to the hdlatency tool (get it from Launchpad), it now has a –quick option to have it only do its tests with 16KB blocks rather than a whole range of sizes. This is much quicker, and 16KB is the InnoDB page size so it’s the most relevant for MySQL/MariaDB deployments. However, I didn’t just remove the other stuff, because it can be very helpful in tracking down problems and putting misconceptions to rest. On SANs (and local RAID of course) you have things like block sizes and stripe sizes, and opinions on what might be faster. Interestingly, the real world doesn’t always agree with the opinions. We Mark Callaghan correctly pointed out when I first published it, hdlatency does not provide anything new in terms of functionality, the db IO tests of sysbench cover it all. A key advantage of hdlatency is  [Read more...]

As I described yesterday, Open Query is doing some tests on SSDs and other devices pretending to be harddisks (SANs, battery-backed RAID controllers, etc). To aid this, I wrote a small tool to test the different kind of I/O operations MySQL would/could do, which is not quite the same as what other general purpose apps would do, and also not what other test tools measure. For instance, it tries Direct I/O as well as fsync() after each write, and also it a range of different I/O block sizes.

In a nutshell, it’s aimed to do what MySQL does, without MySQL! Testing lots of different setups for this particular purpose (even with fantastic tools like MySQL Sandbox) is a complete pest, and changing InnoDB page size requires a recompile. While Percona has tried a larger page size in the past and decided it wasn’t worth it (the default

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