From owner-freebsd-current Thu Mar 23 15:45:17 2000 Delivered-To: freebsd-current@freebsd.org Received: from dan.emsphone.com (dan.emsphone.com [199.67.51.101]) by hub.freebsd.org (Postfix) with ESMTP id 923E137C520 for ; Thu, 23 Mar 2000 15:45:13 -0800 (PST) (envelope-from dan@dan.emsphone.com) Received: (from dan@localhost) by dan.emsphone.com (8.9.3/8.9.3) id RAA67589; Thu, 23 Mar 2000 17:44:38 -0600 (CST) (envelope-from dan) Date: Thu, 23 Mar 2000 17:44:38 -0600 From: Dan Nelson To: Greg Lehey Cc: Poul-Henning Kamp , Alfred Perlstein , Matthew Dillon , current@FreeBSD.ORG Subject: Re: patches for test / review Message-ID: <20000323174438.B59166@dan.emsphone.com> References: <20000320115902.C14789@fw.wintelcom.net> <20211.953581241@critter.freebsd.dk> <20000320152330.A48212@dan.emsphone.com> <20000323152718.C9318@mojave.worldwide.lemis.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.1.5i In-Reply-To: <20000323152718.C9318@mojave.worldwide.lemis.com>; from "Greg Lehey" on Thu Mar 23 15:27:18 GMT 2000 X-OS: FreeBSD 5.0-CURRENT Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG In the last episode (Mar 23), Greg Lehey said: > > Agreed. This is on the Vinum wishlist, but it comes at the expense of > reliability (how long do you wait to cluster? What happens if the > system fails in between?). In addition, for Vinum it needs to be done > before entering the hardware driver. For the simplest case, you can choose to optimize only when the user sends a single huge write(). That way you don't have to worry about caching dirty pages in vinum. This is basically what the hardware RAIDs I have do. They'll only do the write optimization (they call it "pipelining") if you actually send a single SCSI write request large enough to span all the disks. I don't know what would be required to get our kernel to even be able to write blocks this big (what's the upper limit on MAXPHYS)? -- Dan Nelson dnelson@emsphone.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message