Date: Mon, 1 Oct 2001 15:21:09 -0400 From: Carl Schmidt <carl@slackerbsd.org> To: Edwin Groothuis <edwin@mavetju.org> Cc: Bsd Newbie <bsdneophyte@yahoo.com>, freebsd-questions@freebsd.org Subject: Re: accidently pulled the plug... Message-ID: <20011001152108.B72983@slackerbsd.org> In-Reply-To: <20011001212629.K482@k7.mavetju.org> References: <20011001101935.5479.qmail@web20110.mail.yahoo.com> <20011001212629.K482@k7.mavetju.org>
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--24zk1gE8NUlDmwG9 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Oct 01, 2001 at 09:26:29PM +1000, Edwin Groothuis wrote: > > If you have softupdates enabled on your filesystems, then you will probab= ly > have the least problems. >=20 Just a quick point regarding softupdates...softupdates is not the cure for cancer many people like to make it out to be. It protects metadata and that= is all it protects. You are much more likely to lose data (NOTE: not metadata - data) using softupdates if you are doing something disk intensive at the ti= me of the plug pulling or whatever other event causes a not-normal shutdown. Many people are led to believe that softupdates prevents their data from being lost - only metadata as I said before. It says so in the writeup on K= irk McKusick's website (http://www.mckusick.com/softdep/). Just a quick quote f= rom his brief explanation: "Indeed, the ability of soft updates to aggregate many operations previously done individually and synchronously reduces the number of disk writes by 40= to 70% for file-intensive environments (e.g., program development, mail server= s, etc.). In addition to performance enhancement, soft updates can also mainta= in better disk consistency. By ensuring that the only inconsistencies are unclaimed blocks or inodes, soft updates can eliminate the need to run a filesystem check program after every system crash." Most people know this already but a handful (not necessarily you) of newbies tend to think it'll protect them from any data corruption. The unclaimed blocks and/or inodes are probably the result of a almost-complete write to disk that got its inode and almost got the data in there but the machine we= nt down before that could happen. That's my analogy of it anyway - I could be wrong and someone will correct me if I am I'm sure. Just my USD $.02. --=20 Carl Schmidt Just like the pied piper led rats through the streets We dance like marionettes swaying to the symphony of destruction http://slackerbsd.org/ --24zk1gE8NUlDmwG9 Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: PGPfreeware 5.0i for non-commercial use MessageID: AO8CTw8y4a0r6Jp6jP90dLZdZsbBlfWj iQA/AwUBO7jCJCwXrqm5p/cQEQLoNwCg/eeDLOSqdK6GSkjEEGiSRJoAaIIAnR20 Kj5hD40DHkIghccx6kAfqcKa =Lnur -----END PGP SIGNATURE----- --24zk1gE8NUlDmwG9-- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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