Date: Fri, 17 Feb 2012 08:49:41 -0700 (MST) From: Warren Block <wblock@wonkity.com> To: Freddie Cash <fjwcash@gmail.com> Cc: freebsd-stable@freebsd.org, mandrews@bit0.com, 000.fbsd@quip.cz, freebsd@jdc.parodius.com, Pete French <petefrench@ingresso.co.uk> Subject: Re: New BSD Installer Message-ID: <alpine.BSF.2.00.1202170823440.52228@wonkity.com> In-Reply-To: <CAOjFWZ7tfO1097-wnJE5Lt8mtO2FcZhNwHBmYexxnyFi=J0eNg@mail.gmail.com> References: <20120217030806.GA62601@icarus.home.lan> <E1RyLjZ-0009kp-GN@dilbert.ingresso.co.uk> <CAOjFWZ7tfO1097-wnJE5Lt8mtO2FcZhNwHBmYexxnyFi=J0eNg@mail.gmail.com>
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This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. ---902635197-1653418493-1329493022=:52228 Content-Type: TEXT/PLAIN; CHARSET=ISO-8859-15; FORMAT=flowed Content-Transfer-Encoding: 8BIT Content-ID: <alpine.BSF.2.00.1202170837321.52228@wonkity.com> On Fri, 17 Feb 2012, Freddie Cash wrote: > On Fri, Feb 17, 2012 at 3:12 AM, Pete French <petefrench@ingresso.co.uk> wrote: >>> I wasn't aware you could do that. I was only aware that it was the >>> other way around. That (my) misconception seems to also be relayed >>> by others such as Miroslav who said: >> >> Should this not be the recommended way of doing things even for MBR >> disks ? I have a lot of machines booting from gmirror, but we always >> do it by mirroring MBR partitions (or GPT ones). I cant see why you would >> want to do it the other way round in fact. It doesnt gain you anything >> does it ? > > The problem with mirroring partitions is that you thrash the disk > during the rebuild after replacing a failed disk. Potentially, yes. > And the more partitions you have, the worse it gets. One big mirrored partition avoids it, but then there's only one partition. (ad0p2a? Forget I mentioned that.) > If you mirror the device, then the rebuild process only has to rebuild > a single "thing". > > If you mirror 4 partitions on a device, then there will be four > simultaneous, parallel rebuild processes running, thrashing the drive > heads on both devices, killing you I/O throughput and extending the > length of the rebuild. Some queuing logic in the mirror rebuild could avoid that. I am blissfully unaware of how complicated that might be. ---902635197-1653418493-1329493022=:52228--
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