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Speaking to the sys admins we found that the file system where the WAL was written to did not have direct_io and hence all writes were getting buffered. So we enabled direct_io on that FS and now writes are order of magnitude slower (5x times). It seems PG already uses O_DIRECT for WAL. So is the enabling of direct_io in the mount options of the FS totally redundant. It definitely has a serious performance impact. Thanks From: srkrishna@xxxxxxxxxxx To: pgsql-admin@xxxxxxxxxxxxxx Subject: Best setting for wal_sync_method Date: Thu, 7 May 2015 09:36:36 -0400 On RHEL 6.4 which is the best setting for wal_sync_method for write intensive operations. Is the default fdatasync good for all conditions, including reliability. Thanks |
