Date: Sat, 08 Oct 2011 08:18:54 +0000 From: "Poul-Henning Kamp" <phk@phk.freebsd.dk> To: Warren Block <wblock@wonkity.com> Cc: freebsd-current@freebsd.org, Garrett Cooper <yanegomi@gmail.com>, Glen Barber <gjb@freebsd.org>, "Andrey V. Elsukov" <bu7cher@yandex.ru>, Benjamin Kaduk <kaduk@mit.edu>, Arnaud Lacombe <lacombar@gmail.com> Subject: Re: aliasing (or renaming) kern.geom.debugflags Message-ID: <32040.1318061934@critter.freebsd.dk> In-Reply-To: Your message of "Fri, 07 Oct 2011 17:41:59 CST." <alpine.BSF.2.00.1110071734140.4137@wonkity.com>
next in thread | previous in thread | raw e-mail | index | archive | help
In message <alpine.BSF.2.00.1110071734140.4137@wonkity.com>, Warren Block write s: >Since we're talking about this, could you review the usage in the >gmirror section of the Handbook GEOM chapter: > http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/geom-mirror.html > >Seems like that is a valid non-debugging use, to allow the last block to >be written. gmirror and this procedure has several problems: 1. It steals the last sector on the disk. If that sector contained data you lost them, with no notice. Most often it will not, particularly on a freshly installed system, but it is still a bad thing. 2. The paritioning is not fixed up to record the stealing of this sector. I wouldn't be surprised if this could cause confusion down the road. 3. In this case, writing only happens to a single sector, which we assume is not going to be written by anybody else, so apart from #1 and #2 debugflags=16 does not cause any additional damage. This is the kind of usage that makes me sad I ever added that option. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk@FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence.
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?32040.1318061934>