From owner-freebsd-hackers Mon Jan 28 15:42:48 2002 Delivered-To: freebsd-hackers@freebsd.org Received: from wantadilla.lemis.com (wantadilla.lemis.com [192.109.197.80]) by hub.freebsd.org (Postfix) with ESMTP id 9ACEB37B402 for ; Mon, 28 Jan 2002 15:42:42 -0800 (PST) Received: by wantadilla.lemis.com (Postfix, from userid 1004) id 67853782FC; Tue, 29 Jan 2002 10:12:40 +1030 (CST) Date: Tue, 29 Jan 2002 10:12:40 +1030 From: Greg Lehey To: Bernd Walter Cc: Jason Andresen , freebsd-hackers@FreeBSD.ORG Subject: Re: vinum write spanning Message-ID: <20020129101240.E92998@wantadilla.lemis.com> References: <3C556517.CED19C80@mitre.org> <20020128183409.D95936@cicely8.cicely.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20020128183409.D95936@cicely8.cicely.de> User-Agent: Mutt/1.3.23i Organization: The FreeBSD Project Phone: +61-8-8388-8286 Fax: +61-8-8388-8725 Mobile: +61-418-838-708 WWW-Home-Page: http://www.FreeBSD.org/ X-PGP-Fingerprint: 6B 7B C3 8C 61 CD 54 AF 13 24 52 F8 6D A4 95 EF Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG On Monday, 28 January 2002 at 18:34:10 +0100, Bernd Walter wrote: > On Mon, Jan 28, 2002 at 09:49:59AM -0500, Jason Andresen wrote: >> I'm hoping there is an easy answer to this one... >> >> Is there some way vinum can be tickled such that it writes to all disks >> in a plex at once? For instance, say I have a 6 disk RAID5 array >> that I'm writing a 200MB file to. Is there some way I can make >> vinum attempt to write data to all of the drive simultaniously? > > You can't easily increase performance in a single file access case > with more disks. Especialy in the R5 case where you have several > blocks depend on the same parity. Well, in fact it's particularly interesting in the RAID-5 case: then you can write an entire band without having to read first, thus doubling the throughput. The problem with this approach is that FreeBSD is currently limited to an I/O size of 128 kB. A reasonable stripe size for RAID-5 is 300 kB or so, so in Jason's example you'd have to be able to issue an I/O request of 1.5 MB. Until this is possible, there's no point in writing the code (which would be possible, though not trivial). >> If vinum already does that I'm probably just saturating the PCI bus >> and there's nothing more I can do, but it seems like I should have >> a tougher time saturating the bus with 5400RPM drives... > > Vinum is designed for multiple file access which is a more common > situation for a unix system. Well, it tries to be universally useful. But this particular optimization doesn't currently make sense. Greg -- See complete headers for address and phone numbers To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message