Date: Sat, 17 Sep 2005 15:04:15 -0700 From: Danny Howard <dannyman@toldme.com> To: Victor Sudakov <sudakov@sibptus.tomsk.ru> Cc: freebsd-geom@freebsd.org Subject: Re: Create a mirror on disk with valid data Message-ID: <20050917220415.GA73188@ratchet.nebcorp.com> In-Reply-To: <20050917041700.GA46650@admin.sibptus.tomsk.ru> References: <20050916073012.GA31056@admin.sibptus.tomsk.ru> <20050916225527.GT11689@ratchet.nebcorp.com> <20050917041700.GA46650@admin.sibptus.tomsk.ru>
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On Sat, Sep 17, 2005 at 11:17:00AM +0700, Victor Sudakov wrote: > 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? >From what I have read, the gmirror stuff uses a sector of the disk that isn't used at the end, and if you format a disk in such a way that that free sector is unavailable, you can not set up a gmirror. If you find a scenario in which setting up a gmirror destroys data on a disk, then please use send-pr to file a bug, so that that issue can be fixed. But, if your question is "does gmirror do evil things to existing data" then I'll answer that I and others have gmirrored quite a few disks with existing data and I'm not aware that anybody has been bitten by your hypothesis. Thanks, -danny -- http://dannyman.toldme.com/
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