Date: Sat, 17 Sep 2005 11:17:00 +0700 From: Victor Sudakov <sudakov@sibptus.tomsk.ru> To: Danny Howard <dannyman@toldme.com> Cc: freebsd-geom@freebsd.org Subject: Re: Create a mirror on disk with valid data Message-ID: <20050917041700.GA46650@admin.sibptus.tomsk.ru> In-Reply-To: <20050916225527.GT11689@ratchet.nebcorp.com> References: <20050916073012.GA31056@admin.sibptus.tomsk.ru> <20050916225527.GT11689@ratchet.nebcorp.com>
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Danny Howard wrote: > > I have only ever mirrored disks with data on them. Its a question of > bootstrap - does the mirror comes first or does the data you are going > to mirror come first? Suppose the disk has valuable data in the last sector and you are going to create a mirror from this disk. What is going to happen when the last sector is overwritten with the mirror metadata? Your data will be lost, right? Suppose you need to access the last sector, access will be denied, right? > > My crib sheet is at > http://dannyman.toldme.com/2005/01/24/freebsd-howto-gmirror-system/ I have read this document. Have you ever tried to newfs a partition you have mirrored this way? Look at my second mail (screen output), it seems that such a partition cannot be newfs'ed without changing the label, because access to the last sector is denied. Please try to: 1. fdisk and label a disk, create a partition that occupies the whole disk. "disklabel -w ad0s1 auto" will automatically create an "a" partition for you. 2. create a mirror from this disk, e.g. "gmirror label gm1 ad0" 3. newfs /dev/mirror/gm1s1a and see what happens. -- Victor Sudakov, VAS4-RIPE, VAS47-RIPN
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