Bruce Momjian wrote:
Have you seen /src/tools/fsync?
Now that the argument is already open, why postgres choose on linux fdatasync? I'm understanding from other posts that on this platform open_sync is better than fdatasync.
However I choose open_sync. During initdb why don't detect this parameter ?
Regards Gaetano Mendola
These are my times:
kernel 2.4.9-e.24smp ( RAID SCSI ):
Simple write timing:
write 0.011544Compare fsync times on write() and non-write() descriptor:
(If the times are similar, fsync() can sync data written
on a different descriptor.)
write, fsync, close 1.233312
write, close, fsync 1.242086Compare one o_sync write to two:
one 16k o_sync write 0.517633
two 8k o_sync writes 0.824603Compare file sync methods with one 8k write:
(o_dsync unavailable)
open o_sync, write 0.438580
write, fdatasync 1.239377
write, fsync, 1.178017Compare file sync methods with 2 8k writes:
(o_dsync unavailable)
open o_sync, write 0.818720
write, fdatasync 1.395602
write, fsync, 1.351214
kernel 2.4.22-1.2199.nptlsmp (single EIDE disk):
Simple write timing:
write 0.023697Compare fsync times on write() and non-write() descriptor:
(If the times are similar, fsync() can sync data written
on a different descriptor.)
write, fsync, close 0.688765
write, close, fsync 0.702166Compare one o_sync write to two:
one 16k o_sync write 0.498296
two 8k o_sync writes 0.543956Compare file sync methods with one 8k write:
(o_dsync unavailable)
open o_sync, write 0.259664
write, fdatasync 0.971712
write, fsync, 1.006096Compare file sync methods with 2 8k writes:
(o_dsync unavailable)
open o_sync, write 0.536882
write, fdatasync 1.160347
write, fsync, 1.189699
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