Date: Fri, 07 Dec 2001 11:12:57 -0800 From: Kirk McKusick <mckusick@mckusick.com> To: Sheldon Hearn <sheldonh@starjuice.net> Cc: freebsd-arch@FreeBSD.ORG Subject: Re: Using a larger block size on large filesystems Message-ID: <200112071913.fB7JCvf29494@beastie.mckusick.com> In-Reply-To: Your message of "Fri, 07 Dec 2001 13:44:36 GMT." <4.3.2.7.2.20011207134031.00bbfc40@gid.co.uk>
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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
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