Date: Mon, 14 Oct 2013 11:48:18 -0700 From: Charles Swiger <cswiger@mac.com> To: CeDeROM <cederom@tlen.pl> Cc: FreeBSD Questions <freebsd-questions@freebsd.org> Subject: Re: SU+J Lost files after a power failure Message-ID: <F2D0FD23-884F-48D4-865B-CE793E2B4F39@mac.com> In-Reply-To: <CAFYkXj==tiKSAJh3kkCnonsqAaDg_sHYYEUnfLKWLaR-GD-Nzw@mail.gmail.com> References: <525A6831.5070402@gmail.com> <l3gc7e$c91$1@ger.gmane.org> <20131014133953.58f74659@gumby.homeunix.com> <525C1D1C.9050708@gmail.com> <CA%2BtpaK2Pr2po2cQ1yanQK9%2BwLp77SYqYHjxiXaU5FfXwHrkGow@mail.gmail.com> <CAFYkXjn-1wTJcQ4a_fyXCvwh9ukt3%2BdjM2qsMeaH1HhVJNvhiA@mail.gmail.com> <525C2554.7080203@pchotshots.com> <CAFYkXjm8y0Br31_pqRZc0sNFbqCNtKHhjeQuiLXkGT2zxSu0GA@mail.gmail.com> <525C2FBC.4080808@cran.org.uk> <CAFYkXj==tiKSAJh3kkCnonsqAaDg_sHYYEUnfLKWLaR-GD-Nzw@mail.gmail.com>
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On Oct 14, 2013, at 11:33 AM, CeDeROM <cederom@tlen.pl> wrote: > On Mon, Oct 14, 2013 at 7:54 PM, Bruce Cran <bruce@cran.org.uk> wrote: >> On 10/14/2013 6:16 PM, CeDeROM wrote: >>> Isn't there Journal to prevent and reverse such damage? >> >> Unlike other journaling filesystems, UFS+J only protects the metadata, not >> the data itself - i.e. I think it ensures you won't have to run a manual >> fsck, but just like plain old UFS files may be truncated as the journal is >> replayed. > > Thank you for explaining :-) So it looks that it would be sensible to > force filesystem check every n-th mount..? You shouldn't ever need to recheck the filesystem if it was shutdown cleanly. However, it doesn't hurt to fire off an fsck once a year or so just to look for any unexpected issues. > Or to do a filesystem check after crash..? Yes. Without journalling, you'd normally perform the full timeconsuming fsck in the foreground. With journalling, it should be able to do a journal replay to restore the filesystem to an OK state, but sometimes that doesn't restore consistency, in which case it usually fires off a background fsck rather than the foreground fsck. > Are there any flags like that to mark filesystem > unclean and to force fsck after n-th mount? That would assume > disabling journal and soft updates journaling I guess..? /etc/rc.conf should support something like the following to do what you ask: fsck_y_enable="YES" background_fsck="NO" force_fsck="YES" > What would be the best option for best data integrity in case of > crash? That would be helpful for development systems I guess :-) Well, you can use mount -o sync and disable write caching via hw.ata.wc=0 or similar depending on what kind of drives you use. This will cause a massive loss of write performance, but will greatly improve reliability-- i.e. fsync() and such are not as likely to lie about whether bits have made it to disk, even in the face of hardware which lies about ATA_FLUSHCACHE (or SCSI "SYNCHRONIZE CACHE", etc). Regards, -- -Chuck
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