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Last active Mar 12, 2020
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Postgres Filesystem Benchmark of a Corsair MP600 500GB NVMe SSD mounted in a PCIe 2.0 x1 slot (while it would support PCIe 4.0 x4)
$ uname -a
Linux owl 5.5.8-arch1-1 #1 SMP PREEMPT Fri, 06 Mar 2020 00:57:33 +0000 x86_64 GNU/Linux
$ cat /etc/os-release
NAME="Arch Linux"
PRETTY_NAME="Arch Linux"
$ pg_config --version
PostgreSQL 12.2
$ pg_test_fsync
5 seconds per test
O_DIRECT supported on this platform for open_datasync and open_sync.
Compare file sync methods using one 8kB write:
(in wal_sync_method preference order, except fdatasync is Linux's default)
open_datasync 2286.186 ops/sec 437 usecs/op
fdatasync 2216.011 ops/sec 451 usecs/op
fsync 1904.720 ops/sec 525 usecs/op
fsync_writethrough n/a
open_sync 1900.989 ops/sec 526 usecs/op
Compare file sync methods using two 8kB writes:
(in wal_sync_method preference order, except fdatasync is Linux's default)
open_datasync 1137.062 ops/sec 879 usecs/op
fdatasync 2160.299 ops/sec 463 usecs/op
fsync 1896.817 ops/sec 527 usecs/op
fsync_writethrough n/a
open_sync 958.446 ops/sec 1043 usecs/op
Compare open_sync with different write sizes:
(This is designed to compare the cost of writing 16kB in different write
open_sync sizes.)
1 * 16kB open_sync write 1917.688 ops/sec 521 usecs/op
2 * 8kB open_sync writes 957.965 ops/sec 1044 usecs/op
4 * 4kB open_sync writes 487.403 ops/sec 2052 usecs/op
8 * 2kB open_sync writes 194.621 ops/sec 5138 usecs/op
16 * 1kB open_sync writes 97.857 ops/sec 10219 usecs/op
Test if fsync on non-write file descriptor is honored:
(If the times are similar, fsync() can sync data written on a different
write, fsync, close 1884.696 ops/sec 531 usecs/op
write, close, fsync 1891.182 ops/sec 529 usecs/op
Non-sync'ed 8kB writes:
write 576714.823 ops/sec 2 usecs/op
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