How do I gmirror slices?
Rick C. Petty
rick-freebsd at kiwi-computer.com
Tue Feb 6 06:20:21 UTC 2007
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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