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Message-ID: <Pine.LNX.4.44.0501121310140.9212-100000@matrix.coldrain.net> From: bruen at coldrain.net (Stormwalker) Subject: Reality, humor, and history (was Re: MORE CRITICAL FLAWS IN MS WINDOWS EXPLORER Hi Valdis, Must be my age... The synch call writes memory/cache resident data to the appropriate disk files, but does not wait to see if all the dirty buffers in memory have been written to disk before it completes. There is no good way to know if all have files have been updated, except to synch a few times. The haltsys command (Unix V) and shutdown -h issue several synch calls to take care of the problem. Unix today generally issues an update command which calls synch every 30 seconds or so in case of a crash or other sudden, unexpected shutdown (eg fsflush in SVR4). And then there is the potential problem of remote disks, which can cause time delays. The metadata inconsistencies are handled differently, partly by the write order and partly by fsck. cheers, bob (*) My all-time favorite "Close, but no ceee-gar" was the advice column for a Unix journal where the author *remembered* the old "3 syncs before halt" adage - but got it Very Wrong by advising "sync;sync;sync;halt". Bonus points if you can remember (a) the *original* reason for the advice *and* (b) how this version was Very Wrong (there's *multiple* answers for this one ;) -- Dr. Robert Bruen Cold Rain Technologies http://coldrain.net +1.802.579.6288
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