Date: Mon, 14 Oct 2013 13:09:40 -0400 From: Brad Mettee <bmettee@pchotshots.com> To: CeDeROM <cederom@tlen.pl>, Adam Vande More <amvandemore@gmail.com> Cc: David Demelier <demelier.david@gmail.com>, FreeBSD Questions <freebsd-questions@freebsd.org> Subject: Re: SU+J Lost files after a power failure Message-ID: <525C2554.7080203@pchotshots.com> In-Reply-To: <CAFYkXjn-1wTJcQ4a_fyXCvwh9ukt3%2BdjM2qsMeaH1HhVJNvhiA@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>
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On 10/14/2013 12:50 PM, CeDeROM wrote: > On Mon, Oct 14, 2013 at 6:47 PM, Adam Vande More <amvandemore@gmail.com> wrote: >> On Mon, Oct 14, 2013 at 11:34 AM, David Demelier >> <demelier.david@gmail.com>wrote: >>> Why? SU+J is enabled by default. Isn't the purpose of a journaled file >>> system to ensure that any bad shutdown will protect data? >> As already stated, those measures are to preserve fs integrity eg meta data >> is in sync. It doesn't ensure that all the outstanding writes are >> committed to disk in the event of a power outage. > Then why random files gets damaged as well even they are not > accessed/written on power loss? :-) Random files can be affected because the sectors of the hard disk containing the directory entries for those files, not the file data itself, may be damaged (ie: the directory was in the process of being written OR the pointer to that SECTOR was in the process of being written). It doesn't mean a file was in active use, just that a chunk of the disk with data relevant to that file was. Keep in mind, one sector of disk may have data for a dozen files in it (or more). Damage doesn't have to occur because a given file was in use at the time of a crash. If your power grid is prone to failures or blips, I strongly suggest investing in a UPS. Brad
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