From owner-freebsd-hackers Tue Apr 4 14:41:59 1995 Return-Path: hackers-owner Received: (from majordom@localhost) by freefall.cdrom.com (8.6.10/8.6.6) id OAA24037 for hackers-outgoing; Tue, 4 Apr 1995 14:41:59 -0700 Received: from estienne.cs.berkeley.edu (estienne.CS.Berkeley.EDU [128.32.42.147]) by freefall.cdrom.com (8.6.10/8.6.6) with ESMTP id OAA24031 for ; Tue, 4 Apr 1995 14:41:58 -0700 Received: from localhost (localhost [127.0.0.1]) by estienne.cs.berkeley.edu (8.6.11/8.6.9) with SMTP id OAA12675; Tue, 4 Apr 1995 14:40:05 -0700 Message-Id: <199504042140.OAA12675@estienne.cs.berkeley.edu> X-Authentication-Warning: estienne.cs.berkeley.edu: Host localhost didn't use HELO protocol To: "Rodney W. Grimes" cc: wilko@yedi.iaf.nl (Wilko Bulte), peter@bonkers.taronga.com, terry@cs.weber.edu, PVinci@ix.netcom.com, hackers@FreeBSD.org Subject: Re: large filesystems/multiple disks [RAID] In-reply-to: Your message of "Tue, 04 Apr 1995 10:20:52 PDT." <199504041720.KAA07847@gndrsh.aac.dev.com> Date: Tue, 04 Apr 1995 14:40:04 -0700 From: "Justin T. Gibbs" Sender: hackers-owner@FreeBSD.org Precedence: bulk >> >> > RAID does have the negative effect of of having to write 20% more data, >> > thus cutting effective bandwidth by 20%. It is actually worse than >> > this in that all writes must write to at least 2 drives no matter how >> > small they are. The removes some of the benifits of stripping. >> >> And that is why some RAID systems use (battery backed up please ;-) RAM >> caches. This works quite nicely. > >And you find these caches will fill up and some point in a sustained >write test and you end up right back at the 20% performance loss I >was talking about. Is this still true with hardware parity calculation? >Pure stripping of drives always outperforms RAID, you always pay some >price for reliability, and it is usually performance or $$$. > ... >-- >Rod Grimes rgrimes@gndrsh.aac.dev.com >Accurate Automation Company Custom computers for FreeBSD -- Justin T. Gibbs ============================================== TCS Instructional Group - Programmer/Analyst 1 Cory | Po | Danube | Volga | Parker | Torus ==============================================