On Tue, Feb 11, 2014 at 12:20 AM, Marti Raudsepp <marti@xxxxxxxxx> wrote: > This is on Ubuntu 13.10 (kernel 3.11) with XFS (mount ed with noatime, > no other customizations). I managed to track this down; XFS doesn't allow using O_DIRECT for writes smaller than the filesystem's sector size (probably same on other FSes). The XFS filesystem created by the Ubuntu installer uses 4kB sectors, for some weird reason: # xfs_info /dev/sda1 meta-data=/dev/disk/by-uuid/987c0579-bd67-4f80-bbc6-50f975ee4c1d isize=256 agcount=16, agsize=4341104 blks = sectsz=4096 attr=2 [...] Yet the storage stack knows they're 512-byte sectors: # cat /sys/block/sda/queue/logical_block_size 512 # cat /sys/block/sda/queue/physical_block_size 512 A new fresh filesystem also properly uses 512B sectors: # mkfs.xfs /dev/sda5 meta-data=/dev/sda5 isize=256 agcount=4, agsize=489856 blks = sectsz=512 attr=2, projid32bit=0 [...] I will be submitting a patch for pg_test_fsync so it can survive write failures in this situation. ---- I could still use some help with this part... Does anyone have experience in setting up megaraid_sas for reliable fsyncs? > open_datasync 1575.148 ops/sec 635 usecs/op > fdatasync 1460.741 ops/sec 685 usecs/op > fsync 1362.300 ops/sec 734 usecs/op > fsync_writethrough n/a > open_sync 1528.402 ops/sec 654 usecs/op Regards, Marti -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general