From owner-freebsd-arch Fri Dec 7 11:13:24 2001 Delivered-To: freebsd-arch@freebsd.org Received: from beastie.mckusick.com (tserver.conference.usenix.org [209.179.127.3]) by hub.freebsd.org (Postfix) with ESMTP id 8C31537B405 for ; Fri, 7 Dec 2001 11:13:21 -0800 (PST) Received: from beastie.mckusick.com (localhost [127.0.0.1]) by beastie.mckusick.com (8.11.4/8.9.3) with ESMTP id fB7JCvf29494; Fri, 7 Dec 2001 11:13:04 -0800 (PST) (envelope-from mckusick@beastie.mckusick.com) Message-Id: <200112071913.fB7JCvf29494@beastie.mckusick.com> To: Sheldon Hearn Subject: Re: Using a larger block size on large filesystems Cc: freebsd-arch@FreeBSD.ORG In-Reply-To: Your message of "Fri, 07 Dec 2001 13:44:36 GMT." <4.3.2.7.2.20011207134031.00bbfc40@gid.co.uk> Date: Fri, 07 Dec 2001 11:12:57 -0800 From: Kirk McKusick Sender: owner-freebsd-arch@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG Even with only one cylinder group you will have two superblocks. One in the standard location (at sectors 16-32) and one backup in the first cylinder group (at sectors 32-48). The down side is that they immediately follow each other, but there are two copies. The main drawback of 16K/2K for small filsystems that I see is the wasted space (rounding up to 2K rather than 1K) means that you will fill it up faster than you would with 8K/1K. On balance, I do not see either of these as strong enough reasons to special case `small' filsystems though I would not object if you choose to do so. FYA, we had this same debate a bit over a decade ago when we changed the default from 4K/512 to 8K/1K. Obviously, we decided not to special case small filesystems then despite great hand-wringing over what would happen... Kirk McKusick To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message