Date: Tue, 3 Aug 1999 08:12:17 +0200 From: Bernd Walter <ticso@cicely.de> To: Stephen Hocking-Senior Programmer PGS Tensor Perth <shocking@prth.pgs.com> Cc: Greg Lehey <grog@lemis.com>, hackers@FreeBSD.ORG Subject: Re: Adding disks -the pain. Also vinum Message-ID: <19990803081216.B23148@cicely8.cicely.de> In-Reply-To: <199908030416.MAA16945@ariadne.tensor.pgs.com>; from Stephen Hocking-Senior Programmer PGS Tensor Perth on Tue, Aug 03, 1999 at 12:16:06PM %2B0800 References: <19990803133554.S62948@freebie.lemis.com> <199908030416.MAA16945@ariadne.tensor.pgs.com>
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On Tue, Aug 03, 1999 at 12:16:06PM +0800, Stephen Hocking-Senior Programmer PGS Tensor Perth wrote: > > > No, it would cause a higher I/O load. Vinum doesn't transfer entire > > stripes, it transfers what you ask for. With a large stripe size, the > > chances are higher that you can perform the transfer with only a > > single I/O. > > Even if I'm using really large reads? Several month ago I beleaved the same but there are severall points here: - UFS/FFS don't handle clustering over 64k - modern harddisks do preread simply by having a reversed sector layout. - without spindle syncronisation you will have additional latency - vinum don't aggregate access to subdisks, so the transfer to the subdisks is limited by the stripe size. For UFS/FFS there is nothing worth seting the stripesize to low. It is generally slower to acces 32k on different HDDs than to acces 64k on one HDD. Spindle Sycronisation won't bring you that much on modern HDDs - I tried it using 5 Seagate Elite 2.9G (5,25" Full-Height). There was no win using FFS. If you need performance try softupdates. At least for writing it should benefit much from striped partitions. I never realy measured but I was astounished that you can have over 800 transactions/sec on a ccd with 6 striped disks. -- B.Walter COSMO-Project http://www.cosmo-project.de ticso@cicely.de Usergroup info@cosmo-project.de To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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