Am Fri, 23 Jan 2015 08:46:23 +0000 (UTC) schrieb Duncan <1i5t5.dun...@cox.net>:
> Marc Joliet posted on Fri, 23 Jan 2015 08:54:41 +0100 as excerpted: > > > Am Fri, 23 Jan 2015 04:34:19 +0000 (UTC) > > schrieb Duncan <1i5t5.dun...@cox.net>: > > > >> Gareth Pye posted on Fri, 23 Jan 2015 08:58:08 +1100 as excerpted: > >> > >> > What are the chances that splitting all the large files up into sub > >> > gig pieces, finish convert, then recombine them all will work? > >> > > [...] > >> Option 2: Since new files should be created using the desired target > >> mode (raid1 IIRC), you may actually be able to move them off and > >> immediately back on, so they appear as new files and thus get created > >> in the desired mode. > > > > With current coreutils, wouldn't that also work if he moves the files to > > another (temporary) subvolume? (And with future coreutils, by copying > > the files without using reflinks and then removing the originals.) > > If done correctly, yes. > > However, "off the filesystem" is far simpler to explain over email or the > like, and is much less ambiguous in terms of "OK, but did you do it > 'correctly'" if it doesn't end up helping. If it doesn't work, it > doesn't work. If "move to a different subvolume under specific > conditions in terms of reflinking and the like" doesn't work, there's > always the question of whether it /really/ didn't work, or if somehow the > instructions weren't clear enough and thus failure was simply the result > of a failure to fully meet the technical requirements. > > Of course if I was doing it myself, and if I was absolutely sure of the > technical details in terms of what command I had to use to be /sure/ it > didn't simply reflink and thus defeat the whole exercise, I'd likely use > the shortcut. But in reality, if it didn't work I'd be second-guessing > myself and would probably move everything entirely off and back on to be > sure, and knowing that, I'd probably do it the /sure/ way in the first > place, avoiding the chance of having to redo it to prove to myself that > I'd done it correctly. > > Of course, having demonstrated to myself that it worked, if I ever had > the problem again, I might try the shortcut, just to demonstrate to my > own satisfaction the full theory that the effect of the shortcut was the > same as the effect of doing it the longer and more fool-proof way. But > of course I'd rather not have the opportunity to try that second-half > proof. =:^) > > Make sense? =:^) I was going to argue that my suggestion was hardly difficult to get right, but then I read that cp defaults to --reflink=always and that it is not possible to turn off reflinks (i.e., there is no --reflink=never). So then would have to consider alternatives like dd, and, well, you are right, I suppose :) . (Of course, with the *current* version of coreutils, the simple "mv somefile tmp_subvol/; mv tmp_subvol/somefile ." will still work.) -- Marc Joliet -- "People who think they know everything really annoy those of us who know we don't" - Bjarne Stroustrup
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