Date: Wed, 16 Aug 2006 05:50:55 -0700 (PDT) From: "R. B. Riddick" <arne_woerner@yahoo.com> To: Danny Carroll <danny@dannysplace.net>, freebsd-geom@FreeBSD.org Subject: Re: Mirror MBR? Message-ID: <20060816125055.85636.qmail@web30312.mail.mud.yahoo.com> In-Reply-To: <44E30387.5000203@dannysplace.net>
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--- Danny Carroll <danny@dannysplace.net> wrote: > My main question is about the MBR. I dont see anywhere in the doc where > I should put a new boot record on the disk after doing: > If u mirror the whole disk (solution 1) the first sectors should be mirrored like the others (but not the last, which contains disk specific meta data). > dd if=/dev/zero of=/dev/ad0 bs=512 count=79 > What is that good for? Doesn't gmirror synchronize automatically? > Does this mean that the MBR from the mirror gets put onto this first disk? > During boot stages gmirror is not known. All boot programmes (BIOS, stage1, stage2, stage3) use the data on the first sectors of the disk, slice and/or partition) for booting... When the system mounts the root file system gmirror is needed and used if proper configured (that would be: gmirror module loaded before boot or compiled to kernel). > I ask because, I need to know what should happen when I need to replace > a disk. > If I were u, I would simulate all (or the imporant) scenarios: E. g.: 1. One disk failed while power is off... 2. One disk is added while power is off... 3. One disk recovers after power on (e. g. after a power failure, which corrupted the mirror)... If you are really busy as a bee, you could try putting a geom_nop device into the mirror and see, what happens if u suddenly configure the nop-disk to behave like a really bad disk... :-) > I know that after replacing the disk I should probably have to do > something like this: (Assume ad0 is the new disk) > > gmirror configure -a gm0 > What is that good for? I run my geom_mirrors always in AUTO_SYNC mode... E. g. in case of a power failure or so... > But does that guarantee me that if ad0 fails, then I still have a > bootable system (assuming bios knows to boot of ad1). > Yes, it should. At least if the BIOS is smart enough to look for another disk if the first one mentioned in BIOS configuration behaves like a dead disk... I tested it on my box and I think, that it worked fine... <-- this was no sworn testimony... -Arne --- Arne likes "Kentucky Fried Movie" (especially "A fistful of yen") :-) __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com
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