Received: from maia.hub.org (maia-3.hub.org [200.46.204.243]) by mail.postgresql.org (Postfix) with ESMTP id 5B19965A1FC for ; Thu, 10 Jun 2010 19:15:38 -0300 (ADT) Received: from mail.postgresql.org ([200.46.204.86]) by maia.hub.org (mx1.hub.org [200.46.204.243]) (amavisd-maia, port 10024) with ESMTP id 01709-01 for ; Thu, 10 Jun 2010 22:15:28 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from momjian.us (momjian.us [70.90.9.53]) by mail.postgresql.org (Postfix) with ESMTP id EDB9465A095 for ; Thu, 10 Jun 2010 19:15:29 -0300 (ADT) Received: (from bruce@localhost) by momjian.us (8.11.6/8.11.6) id o5AMFTA19322; Thu, 10 Jun 2010 18:15:29 -0400 (EDT) From: Bruce Momjian Message-Id: <201006102215.o5AMFTA19322@momjian.us> Subject: Re: fsync tests In-Reply-To: To: RBN Date: Thu, 10 Jun 2010 18:15:29 -0400 (EDT) CC: pgsql-admin@postgresql.org X-Mailer: ELM [version 2.4ME+ PL124 (25)] MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="US-ASCII" X-Virus-Scanned: Maia Mailguard 1.0.1 X-Spam-Status: No, hits=-1.91 tagged_above=-10 required=5 tests=BAYES_00=-1.9, T_RP_MATCHES_RCVD=-0.01 X-Spam-Level: X-Archive-Number: 201006/94 X-Sequence-Number: 34872 RBN wrote: > I ran test_fsync on a local ext 3 partition and on a raid jfs SSD array > 8x32GB RAID10. The local disk returned quickly and gave what looks like > acceptable results. However, the RAID looks pretty bad. Any one have any > idea why fsync would take so long on an SSD RAID 10. As the original author of the test, all I can say is that those numbers look bad. :-( --------------------------------------------------------------------------- > > > LOCAL DISK > Simple write timing: > write 0.005460 > > Compare 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 0.072429 > write, close, fsync 0.075627 > > Compare one o_sync write to two: > (o_sync unavailable) > (o_dsync unavailable) > write, fdatasync 0.075907 > write, fsync, 0.076320 > > Compare file sync methods with 2 8k writes: > (o_dsync unavailable) > write, fdatasync 0.108367 > write, fsync, 0.108659 > > > > RAID 10 SSD jfs > Simple write timing: > write 0.004843 > > Compare 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 95.546382 > write, close, fsync 51.407276 > > Compare one o_sync write to two: > (o_sync unavailable) > (o_dsync unavailable) > write, fdatasync 10.999764 > write, fsync, 80.696959 > > Compare file sync methods with 2 8k writes: > (o_dsync unavailable) > write, fdatasync 111.931881 > write, fsync, 99.329298 -- Bruce Momjian http://momjian.us EnterpriseDB http://enterprisedb.com + None of us is going to be here forever. +