Date: Wed, 18 Feb 1998 19:50:11 +0100 (MET) From: Wilko Bulte <wilko@yedi.iaf.nl> To: shimon@simon-shapiro.org Cc: curt@kcwc.com, freebsd-scsi@FreeBSD.ORG Subject: Re: getting oriented with RAID Message-ID: <199802181850.TAA01578@yedi.iaf.nl> In-Reply-To: <XFMail.980218001054.shimon@simon-shapiro.org> from Simon Shapiro at "Feb 18, 98 00:10:54 am"
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As Simon Shapiro wrote... > > On 17-Feb-98 Curt Welch wrote: > > ... > > I'd say that four 4.5gig drives in a RAID 0+1 config will > > perform better than two 9gig drives in a RAID 1 config. > > Both of these configs give you the same overall disk space > > (9gig), but with the smaller drives striped together, you > > spread the IO over more spindles (4 vs 2) and therefor you > > will get better performance. So, in this case 0+1 is better > > than just 1. > > For most random access applications, the more heads the marrier. > One of the biggest secrets in RDBMS benchmarking is disk optimization. > What you see, almost universally, is that, for high-end systems, the > benchmarking engineer rarely uses more than 300MB per drive, and rarely > puts more than 4-6 drives on one SCSI bus. You want to stay on the outside of your ZBR platters to achieve the highest datarates. > Unless you want to do what I used to do for a living for many years (compute > all this nonsense), just experiment with drives, busses, stripe sizes, > amount of cache, cache utilization, host cache vs. DPT cache, etc. Not to forget write-back caching (with battery backup please) _ ______________________________________________________________________ | / o / / _ Bulte email: wilko @ yedi.iaf.nl http://www.tcja.nl/~wilko |/|/ / / /( (_) Arnhem, The Netherlands - Do, or do not. There is no 'try' --------------- Support your local daemons: run [Free,Net,Open]BSD Unix -- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message
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