Date: Mon, 30 Jun 2008 19:04:00 +0200 From: Roland Smith <rsmith@xs4all.nl> To: Jim <stapleton.41@gmail.com> Cc: freebsd-questions@freebsd.org Subject: Re: filesystem information Message-ID: <20080630170400.GB65282@slackbox.xs4all.nl> In-Reply-To: <80f4f2b20806300930p67ca1fd5xf9ad59d16889df36@mail.gmail.com> References: <80f4f2b20806300401x71483882x8e9a6cf919f1ff9@mail.gmail.com> <20080630073059.be11304d.wmoran@potentialtech.com> <80f4f2b20806300930p67ca1fd5xf9ad59d16889df36@mail.gmail.com>
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--UHN/qo2QbUvPLonB Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Jun 30, 2008 at 12:30:38PM -0400, Jim wrote: > On Mon, Jun 30, 2008 at 7:30 AM, Bill Moran <wmoran@potentialtech.com> wr= ote: > > In response to Jim <stapleton.41@gmail.com>: > > > >> I have a computer that is in a situation where it is losing power > >> occasionally. All but one of the filesystems are going along fine. > >> Once file system seems to lose data on a power outage. Even if it only > >> reads a file, and doesn't write it, it may still lose a file (ex, > >> about half the audio files on my xmms playlist, a couple data files in > >> my wine directory that, to my knowledge, are unlikely to be written > >> after they are first installed). > >> > >> What I'd like to do is get an output of the flags and options on my > >> filesystems to see what is different between that filesystem and the > >> others. Any suggestion on how to do that? This particular FS has > >> lasted through several rebuilds since it doesn't hold OS critical > >> stuff, just data files. > > > > tunefs -p and/or dumpfs -m > > > >> Any suggestions? > > > > Sounds like you're on the right track with hunting this down. Perhaps > > turn softupdates off and mount the filesystem sync if you're seeing > > lots of power outages. Ans set 'hw.ata.wc=3D"0"' in /boot/loader.conf to stop the drives from caching writes. > Thanks, it looks like the 'good' filesystems have softupdates off > (except one), and the one the broke has it off. I thought softupdates > were supposed to fix this? Is gjournal a better solution? Is 'just use > neither' a better solution?=20 WRT softupdates/gjournal, see below. In case of frequent power outages, I guess the right answer is "get a UPS". :) Without a UPS nothing can protect you against power outages. Even when running the filesystem with the sync flag and setting ATA devices to write-through the cache cannot guarantee you won't lose data. If the power fails when a write is in progress, you're screwed. A proper UPS with monitoring software will give your system time to shut down properly (finishing writes, unmounting etc) before its battery runs ou= t.=20 > Any reference material on the subject See http://en.wikipedia.org/wiki/Soft_updates : Instead of duplicating metadata writes in a journal, soft updates work by properly ordering the metadata writes to guarantee consistency after a crash. Like journaling, soft updates do not guarantee that no data will be lost, but do make sure the filesystem is consistent In FreeBSD softupdates have a longer track record than journaling.=20 Roland --=20 R.F.Smith http://www.xs4all.nl/~rsmith/ [plain text _non-HTML_ PGP/GnuPG encrypted/signed email much appreciated] pgp: 1A2B 477F 9970 BA3C 2914 B7CE 1277 EFB0 C321 A725 (KeyID: C321A725) --UHN/qo2QbUvPLonB Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.9 (FreeBSD) iEYEARECAAYFAkhpEgAACgkQEnfvsMMhpyW/iQCeLWHeTa31BsG7R8XOv0AdVH2B k8AAoJH5HzzwIy9NKDlqZEfMR8eMHI1d =9ua7 -----END PGP SIGNATURE----- --UHN/qo2QbUvPLonB--
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