Christoph Anton Mitterer posted on Mon, 19 Sep 2016 21:45:46 +0200 as excerpted:
> On Mon, 2016-09-19 at 17:27 +0200, David Sterba wrote: > >> > For specific features: >> > - Autodefrag >> > - didn't that also cause reflinks to be broken up? >> >> No and never had. > > Absolutely sure? One year ago, I was told that at first too so I started > using it, but later on some (IIRC) developer said auto-defrag would also > suffer from it. AFAIK it was Hugo that said he looked into that, and that (if I'm representing it correctly) autodefrag breaks reflinks and triggers space- using duplication much as defrag does, but that it does it on a much smaller scale, since it (1) only triggers when some parts of a file are being rewritten anyway, thus breaking the reflink for those specific parts of the file due to COW (COW1 on otherwise NOCOW files) in any case, and (2) unlike defrag, doesn't rewrite and thus break the reflinks on entire files, just somewhat larger extents than the pure rewrite by itself without autodefrag would. Thus making the reflink-breaking and duplication effect of autodefrag there, but relatively quite small compared to on-demand per-file defrag. -- Duncan - List replies preferred. No HTML msgs. "Every nonfree program has a lord, a master -- and if you use the program, he is your master." Richard Stallman -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
