On Sunday 2012-12-09 11:41, Roman Mamedov wrote: >> >> Absolutely. COW snapshots cause severe fragmentation (it's >> in their nature). > >CoW filesystem incurs fragmentation by its nature, not specifically snapshots. >Even without snapshots, rewriting portions of existing files will write the >new blocks not over the original ones, but elsewhere, thus increasing >fragmentation. Right, of course. In the "normal" case, the originals are deleted at some point, so the length of the CoW "chain" should be bound. However, with snapshots, there is, I wager to say, no limit to the chain length, so defragmenting a file also becomes more work. One can of course use rsync without --inplace, which does a full file copy-up if the file has changed, which essentially disables CoW, and thus reduces fragmentation. Unfortunately, not all copy operations on one's machine do use rsync, so perhaps it would be nice to have this as a subvolume mount option as well. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
