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Using Postgres pg_test_fsync tool for testing low latency writes

Here’s a useful tool for quickly testing whether a disk (or a cloud block store volume) is a good candidate for your database WAL/redo logs and any other files that require low latency writes. The pg_test_fsync tool is bundled with standard Postgres packages, so no extra installation is needed. You don’t actually have to use Postgres as your database, this tool’s output is universally valuable for any workload requiring fast writes. - Linux, Oracle, SQL performance tuning and troubleshooting - consulting & training.

Here’s a useful tool for quickly testing whether a disk (or a cloud block store volume) is a good candidate for your database WAL/redo logs and any other files that require low latency writes. fdatasync is faster than fsync or the O_SYNC flag used at file open, as it can avoid waiting for the additional filesystem journal I/Os (when overwriting blocks that already exist on disk). Note that this tool failed with an “Invalid argument” error in the end, this is because that particular disk does not support I/O sizes under 4kB (scroll up to see the lsds output and its HWSEC field).

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