Date: Sat, 27 Sep 2003 11:53:05 +0930 From: Greg 'groggy' Lehey <grog@FreeBSD.org> To: Martin Brecher <listuser@mb-itconsulting.com> Cc: freebsd-questions@freebsd.org Subject: Re: Vinum RAID5 speed question Message-ID: <20030927022305.GG16008@wantadilla.lemis.com> In-Reply-To: <3F742161.7080403@mb-itconsulting.com> References: <3F742161.7080403@mb-itconsulting.com>
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--u0lqphHC8S+ob1K0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Friday, 26 September 2003 at 13:22:09 +0200, Martin Brecher wrote: > Hi, - > > I plan on setting up a vinum RAID5 array of three 120GB IDE disks. The > disks will be attached to two Promise 100 TX2 controllers, on which two > other disks are residing, too. > > The following questions have come to my mind: > > 1. I thought about getting disks with 8MB cache. Does the bigger cache > size affect performance in a RAID5 scenario? Possibly. > 2. Currently I'm running a RAID5 with 4 older 5400rpm disks in that > machine, and write speeds are around 3MB/s. I guess that several people > here are running vinum RAID5 with current IDE disks, so what throughput > can I expect from the new planned setup? Difficult to say. Possibly a little more. > 3. The volume is meant for storing all kinds of files with all kinds of > sizes. My current setup has a blocksize of 489kb. From other people's > experience, what blocksize might bring the best results for such general > purpose? That probably bases on a recommendation I made some years ago, before people pointed out the errors of my ways. You'll get fractionally (and possibly not measurably) better performance if the stripe size is a multiple of the block size. Since that's 16 kB nowadays, a stripe size of 496 kB might be better. =20 > 4. Any other advice would be welcome, of course. :-) Well, the obvious one is that RAID-5 is not intended for writing :-) Greg -- When replying to this message, please copy the original recipients. If you don't, I may ignore the reply or reply to the original recipients. For more information, see http://www.lemis.com/questions.html See complete headers for address and phone numbers. NOTE: Due to the currently active Microsoft-based worms, I am limiting all incoming mail to 131,072 bytes. This is enough for normal mail, but not for large attachments. Please send these as URLs. --u0lqphHC8S+ob1K0 Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.0 (FreeBSD) iD8DBQE/dPSJIubykFB6QiMRAs1VAJ0Zen0QVZwKD1ss0HbokRSlLRvOigCfZvJm 380rpS6XUDMPXQvVsPZFBXM= =nZ2O -----END PGP SIGNATURE----- --u0lqphHC8S+ob1K0--
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