Date: Fri, 23 Sep 2005 07:32:37 -0500 From: Eric Anderson <anderson@centtech.com> To: Francisco <francisco@natserv.net> Cc: Jeff Tchang <jeff.tchang@gmail.com>, freebsd-performance@freebsd.org Subject: Re: 3Ware 7500-4 Slow Message-ID: <4333F5E5.80709@centtech.com> In-Reply-To: <20050922215326.B50836@zoraida.natserv.net> References: <63f9d26505090417183dff415e@mail.gmail.com> <431C683B.1080803@mac.com> <20050922215326.B50836@zoraida.natserv.net>
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Francisco wrote: > On Mon, 5 Sep 2005, Chuck Swiger wrote: > >> Small writes are pretty much the worst-case scenario for RAID-5, > > > Such as mail servers? > How about for a DB server which is mostly read only? > >> normal to see a very significant performance drop-- by up to an order >> of magnitude-- from the performance of a bare drive. > > > > At which point Raid 5 starts to perform better? > 6,8,10 drives? > > > How about RAID 10 for a DB server? > I have been trying to convince the "powers that be" that SCSI would be > much better.. but the price difference is just too astronomical for the > capacities we need (500GB to 2 TB) > > Even 10K RPM IDE drives seem like would be a problem since they are > mostly small in size. I have a 16 disk SATA (WD Raptor 74GB drives) build with a RAID0+1 (maybe called a RAID10 by others) connected via fiber channel, and I get extremely fast data rates with it. A RAID0+1 is much faster at writes than a RAID5, and I believe faster at reads too. I've gotten 180-190MB/s from this disk, which is probably the most I could ask for on a 2gbit connection. For databases, this is a great solution (I have a MySQL db running on one - never disk bound, ever). I bought the array here: http://www.acnc.com They are FreeBSD friendly (and even support it too!) and have tools for FreeBSD as well as all the other OS's too. I've had great luck so far with them. One recommendation - get 1GB cache on the boxes - you'll see huge performance improvements for very little cost. Eric -- ------------------------------------------------------------------------ Eric Anderson Sr. Systems Administrator Centaur Technology Anything that works is better than anything that doesn't. ------------------------------------------------------------------------
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