Date: Sat, 17 Sep 2011 10:34:12 +0300 From: Daniel Kalchev <daniel@digsys.bg> To: Rich <rincebrain@gmail.com> Cc: Jason Usher <jusher71@yahoo.com>, "freebsd-fs@freebsd.org" <freebsd-fs@freebsd.org> Subject: Re: ZFS obn FreeBSD hardware model for 48 or 96 sata3 paths... Message-ID: <72A6ABD6-F6FD-4563-AB3F-6061E3DD9FBF@digsys.bg> In-Reply-To: <CAOeNLuprLpbMppZ_Wd47Ph_VDXbaEUd2r%2B1Fs%2B1XcJfx_AcNnw@mail.gmail.com> References: <1316222526.31565.YahooMailNeo@web121205.mail.ne1.yahoo.com> <CAHcKe7kfdirJL-vPw=pnFvtzo7ZouDQNPkLVbKs_s35Amz40NQ@mail.gmail.com> <4E742E5C.2010900@freebsd.org> <CAOeNLuprLpbMppZ_Wd47Ph_VDXbaEUd2r%2B1Fs%2B1XcJfx_AcNnw@mail.gmail.com>
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On Sep 17, 2011, at 08:45 , Rich wrote: > The 9201-16e or similar would do fine for 6 Gbit SAS rates if you > don't want hardware RAID. >=20 > To get full bandwidth SATA 3 from 48/96 drives, that's 750 MB/s * 8/10 > (8 data bytes per 10 bytes transmitted raw - SATA 3 does an 8b10b > encoding) ~ 600 MB/s * 48/96 =3D 28800/57600 MB/s >=20 There is not single magnetic drive on the market that can saturate SATA2 = (300 Mbps), yet. Most can't match even SATA1 (150 MBps). You don't need = that much dedicated bandwidth for drives. If you intend to have 48/96 SSDs, then that is another story, but then I = am doubtful a "PC" architecture can handle that much data either. If you are looking gat IOPS rather than raw throughput, then by all = means consider (more) SSDs. You may also consider using 2.5" SAS drives = that will be much more compact and less power hungry. The LSI2008 = controllers will manage both SATA and SAS drives (at the same time, in = the same zpool). Memory is much more expensive than SSDs for L2ARC and if your workload = permits it (lots of repeated small reads), larger L2ARC will help a lot. = It will also help if you have huge spool or if you enable dedup etc. = Just populate as much RAM as the server can handle and then add L2ARC = (read-optimized). Daniel=
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