Date: Tue, 6 Feb 2007 00:20:17 -0600 From: "Rick C. Petty" <rick-freebsd@kiwi-computer.com> To: Hansa <mythtv@logic-q.nl> Cc: freebsd geom <freebsd-geom@FreeBSD.ORG> Subject: Re: How do I gmirror slices? Message-ID: <20070206062017.GA50717@keira.kiwi-computer.com> In-Reply-To: <LHEFLGAENILPPDJIHADOOEJNCFAA.mythtv@logic-q.nl> References: <20070129153115.GA36446@keira.kiwi-computer.com> <LHEFLGAENILPPDJIHADOOEJNCFAA.mythtv@logic-q.nl>
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On Mon, Jan 29, 2007 at 05:28:38PM +0100, Hansa wrote: > > > > It's not really outside the file system, it appears at the > > beginning of the > > file system. It's 8KB for UFS1 and 64KB for UFS2. Not only > > that, but that > > 8K or 64K chunk is open/unused at the front of every superblock, that is: > > for every cylinder group, IIRC. > > Is that why fdisk doesn't touches the first 8/64KB before the first slice? > > Offset Size(ST) End Name PType Desc Subtype Flags > > 0 63 62 - 12 unused 0 > 63 12578832 12578894 ad4s1 8 freebsd 165 No, that's actually 63 * 512 = 31.5k. This space is reserved for legacy boot code. FreeBSD skips 8/64KB starting on the slice, in addition to wasted space by the MBR, etc. Actually I think the reason for the 63 is the maximum number of heads times sectors, so the slice is on an even cylinder. Nowadays cylinder/heads/sectors are meaningless. -- Rick C. Petty
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