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You benchmarked a compressed filesystem against uncompressed filesystems and are wondering why the compressed filesystem is slower?
by xi- 9y ago
You benchmarked a compressed filesystem against uncompressed filesystems and are wondering why the compressed filesystem is slower?
- acdha 9y agoThat's specifically incorrect: the results showed that the compressed ZFS was slower on pgbench and faster on TPC-B. It's also generically an unwise assumption because you have to know how fast the compression is compared to disk I/O. If, like almost all servers these days, you have more CPU than I/O capacity the compression overhead will often be buried in the I/O latency and if the data compresses well it it's easy to have it be faster because the I/O savings is greater than the CPU. Since LZ4 was designed to be very fast, that seems like a reasonable bar to hit — I see single-core performance on old desktops in the 1.8+GB/s range.