Date: Wed, 21 May 2014 19:05:01 +0100 From: Matthew Seaman <matthew@FreeBSD.org> To: freebsd-performance@freebsd.org Subject: Re: FreeBSD 10 and PostgreSQL 9.3 scalability issues Message-ID: <537CEACD.8090701@FreeBSD.org> In-Reply-To: <sig.02184fa928.F0529F5B-72EC-4E68-A4BD-75276C70AC1C@chittenden.org> References: <5327B9B7.3050103@gmail.com> <2610F490C952470C9D15999550F67068@multiplay.co.uk> <532A192A.1070509@gmail.com> <assp.0155c70d29.23ED6415-945D-4DF5-90DD-2F2CD7E198AF@chittenden.org> <f4ead73a-fae2-4eac-8499-3cf630eb3d31@googlegroups.com> <CAJ-VmomVOWFb7X5s-amRX7QFzbmT6Kt6bB9gaPVv2_hGx1OS5g@mail.gmail.com> <572540F9-13E4-4BA9-88AE-5F47FB19450A@pingpong.net> <CAJKO3mUTwgiQenSLYfOxHrZxuPQ9kvUPC44MrbLjvpLE=toZQA@mail.gmail.com> <1BC3D447-2044-4AB8-B183-B83957BC9112@pingpong.net> <CAJKO3mX5KA8HZ5tQGTyOgfKbS6HvUvYH-gvzeewTkh3nWz=NRg@mail.gmail.com> <1473AF7C-B190-4CD4-B611-BA4090A081CB@pingpong.net> <sig.02184fa928.F0529F5B-72EC-4E68-A4BD-75276C70AC1C@chittenden.org>
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This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --OtaoFqCRpb7S0cvx3pgqWm3nsT3B7GROf Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable On 21/05/2014 18:17, Sean Chittenden wrote: >> I did some tests with zfs, and results where appallingly bad, but that= was with db size > ram.=20 >> >=20 >> > I think the model used by PostgreSQL, as most databases, are very di= sk block centric. Using zfs makes it hard to get good performance. But th= is was some time ago, maybe things have improved.=20 > I have some hardware that I ran with last week wherein I was *not* able= to reproduce any performance difference between ZFS and UFS2. On both UF= S2 and ZFS I was seeing the same performance when using a a RAID10 / set = of mirrors. I talked with the Dragonfly folk who originally performed the= se tests and they also saw the same thing: no real performance difference= between ZFS and UFS. I ran my tests on a host with 16 drive, 10K SAS, 19= 2GB RAM. I also created a kernel profiling image and ran the 20 concurren= t user test under kgprof(1), dtrace, and pmcstat and have the results ava= ilable: >=20 > http://people.freebsd.org/~seanc/pg9.3-fbsd10-profiling/ >=20 > There are some investigations that are ongoing as a result of these fin= dings. The dfly methodology was observed when generating these results. S= tay tuned. -sc >=20 I'm not sure that the ZFS vs UFS2 question is at the core of the performance problem. We're definitely seeing marked slowdowns between Pg 9.2 and 9.3 on UFS2 (RAID10 + Dell H710p (mfi) raid controller with 1GB NVRAM) In our case the DB size is significantly bigger than RAM, and we also run with a large (3GB) work mem, which seems to exacerbate the slow-down effect. Cheers, Matthew --=20 Dr Matthew J Seaman MA, D.Phil. PGP: http://www.infracaninophile.co.uk/pgpkey --OtaoFqCRpb7S0cvx3pgqWm3nsT3B7GROf Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG/MacGPG2 v2.0.20 (Darwin) Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQJ8BAEBCgBmBQJTfOrOXxSAAAAAAC4AKGlzc3Vlci1mcHJAbm90YXRpb25zLm9w ZW5wZ3AuZmlmdGhob3JzZW1hbi5uZXQ2NTNBNjhCOTEzQTRFNkNGM0UxRTEzMjZC QjIzQUY1MThFMUE0MDEzAAoJELsjr1GOGkATwOEP/jfYOhm6Tz/YzWPtPFAtrd6F gA5EEZ/KxGOxjPUIGhK3+uK6MhxSsDohO7cLWmz2MJd5PXv6scKOgsW7bvFwC0Lp z6GY5LhfH+x3W0Rx4vtsTWaVLz7QBABkNziiSNcux5sc3vBMn0QMEis6req4smRX Lz63WZSkTbrX63fxbTNwyTa0bd0ySzqCDbOA+ggVOgtxwzVwMC9+Y5YJhddmuWbO O4xXXghUKneYVHeMQ4dn5lsVa0t+3s//PASnwCn2aEK5cDSfGUE3jtfLHyxkgPPq XHnmVfbPZ93rlbKI0JBxK7bOkdmXu0J+DeEl8EadjudoO314Kopn5kJ1JoTs3pPj u+AuMG0xcbSUDzhCbE4a5wpdxg3OfC9gxmVeXfVNTfRo9N+gJdorp2lx9bMT/jXJ bTXgw5ZZWuRlZlBhOgzT6W/ta1lX3ZcNDpsOGrFNw4ASLo0RYf1NViC5oUhR0y3n AtToaBlMObmIavPBb0tdiZH+EWbQdRMwt3+bCveDruMx+xHzgLtvpZeP+GqAwG6M ZfAYha/ypLEUq6jYDNEd+Pl/+5MkTAsMulL6gzLVYn+D/RYTssO8sBTHRLvbHE4E 5appLQhjFbn0ZjKamGboIdqObtpJOln5M7jE+hcXMygtzVMIbApYGqxPZ5j4jL+A ZMW6beR+1pwAK6mqgfdj =p4Wy -----END PGP SIGNATURE----- --OtaoFqCRpb7S0cvx3pgqWm3nsT3B7GROf--
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