Hi,
FWIW, I have compared IOPS over different ioengines when normalized for
the resulting CPU load:
https://github.com/oberstet/scratchbox/raw/master/cruncher/engines-compared/normalized-iops.pdf
Takeaway for me was:
- libaio achieves 9.5 mio 4k randread at lowest load
- all sync engines are much more costly (rgd CPU load)
- psync is better than sync
More conclusions:
- Linux MD (RAID-0!) comes at a massive collapse of performance
- it's sad that PostgreSQL doesn't use pread/pwrite
Cheers,
/Tobias
PS:
1. I still want to try sdpk.io/fio plugin (thx Andrey!)
2. I had troubles with the mmap engine (bogs down the machine, behaves
strangely)
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