Date: Wed, 9 Sep 2015 14:42:53 +0100 From: Matthew Seaman <matthew@FreeBSD.org> To: freebsd-questions@freebsd.org Subject: Re: Storage question Message-ID: <55F0375D.4070608@FreeBSD.org> In-Reply-To: <55F031A0.40500@hiwaay.net> References: <55EF3D23.5060009@hiwaay.net> <20150908220639.20412cbd@gumby.homeunix.com> <55EF5409.8020007@yahoo.com> <55EFC2DA.3020101@hiwaay.net> <08B351DD-AA48-4F30-B0D6-C500D0877FB3@lafn.org> <55F02DC8.7000706@hiwaay.net> <20150909150626.5c3b99e5.freebsd@edvax.de> <55F031A0.40500@hiwaay.net>
next in thread | previous in thread | raw e-mail | index | archive | help
This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --4euMknfqB1bE9e8PNIQvXW9DIOaf4NcPP Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: quoted-printable On 2015/09/09 14:16, William A. Mahaffey III wrote: > I like ZFS in principal (it's one of the things that attracted me to > FreeBSD about a year ago), but, as someone else noted, it seems to > require lots of RAM & possibly CPU for best effect. The MythTV box is a= n > AMD A4-5000, 1.5 GHz quad-core jaguar, w/ 16 GB of RAM, which isn't > especially robusto by today's standards, so I am staying w/ UFS. Actually, ZFS's RAM requirements may not be as gargantuan as all that. Despite its reputation for gobbling up all that's available and asking for more, it doesn't have to be that way. What takes up the space are the filesystem caches, and how much you need for those depends absolutely on your usage patterns. It's certainly possible to run ZFS on a pretty small-memory machine just so long as you don't expect to chew through hundreds of files every minute. Also, 16GB really isn't considered small except by people dealing with top of the line servers. If your MythTV usage consists mostly of streaming fairly large files over the network, then in fact, you won't really win much from caching. The files are probably too big to cache entirely in RAM and when you stream them, you'll read or write them once and then not revisit them until the next time you watch whatever it was. So you might as well turn off the cache for those, reduce the space allocated for ARC and find you can live happily in a relatively small amount of memory. ZFS is also not slow for this sort of sequential access -- you'll get overhead for checksumming and compression (but compression can be an overall win for IO throughput, simply by reducing the amount of work the drives have to do) -- but its nothing that any reasonable CPU from the last 5 or so years can't take in its stride. You could certainly run ZFS successfully on the machine you describe, but you'ld have to tune it carefully and run some decent benchmarks if you wanted to ensure the best possible results. Cheers, Matthew --4euMknfqB1bE9e8PNIQvXW9DIOaf4NcPP Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Comment: GPGTools - https://gpgtools.org iQJ8BAEBCgBmBQJV8DdjXxSAAAAAAC4AKGlzc3Vlci1mcHJAbm90YXRpb25zLm9w ZW5wZ3AuZmlmdGhob3JzZW1hbi5uZXQxOUYxNTRFQ0JGMTEyRTUwNTQ0RTNGMzAw MDUxM0YxMEUwQTlFNEU3AAoJEABRPxDgqeTnkV8P/iW7pzDYMBXviBLZzWd8r+rs 2G7GLfLC0I0O4dZQn2L9g9Ofcr0hmEcUR8qQ+yz1+RD+v1SBsHU/IgU3NOSpu+uB IzH97j1meEABBCf/lpciQVcd0mMBzIdc1prC8la6jC8dW2z52Muhb1gQVea+NEH4 THvZUc/qI06B3Sk8i6edKjmriQalQEqdjTz1GA+AAULD0wIryzpXNZEfUQd48CEq vt9vSUp5tX17Y2mBlcWay/1w7faDhzGdzZ0KsKsPt1vvQrKGgk6ZPNGh/fXK1tyK sp7X2oAPwhZydCjJZ83PNgLcEU/8kyX45pKPZ+ComPvyBK8lpX0AksPiHLEE/czj DPuF1eid8KGu7lp1uhHpu3tbX7YGPIH8ya10w3lXnVnzmsOyc7IjwJSYQP4FOuuP 4J+UBMc8dxug86jhBlQjihNb6PpJmJ2C+g3v9PwNBzltK0vX72oERkobkS7GbB1l P58V5ltBTjYO9AkuSaszFiuzbBc5hgfL0///2eQH3Nd2ujTtSgxnUeK+PNNT01se 8YMbQBgaXiU/1zqParbbq+K5uopPVc2+EiactVPQElOz/PGMcQLxeEEtArvhxiHT nO4ngsQ+bWJBvcaokVkcH4nEKVvjfu+4meFVoN15TTJQrJAUoRcu08GD3WAXkh/L EXnRyRdzAXnrga4GeoEH =9V+h -----END PGP SIGNATURE----- --4euMknfqB1bE9e8PNIQvXW9DIOaf4NcPP--
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?55F0375D.4070608>