Copying files shouldn't introduce latency in your desktop experience. Moving files should be throttled.
So apparently, there's another cache that can be enabled at mount time. It's the inode_cache.
It'll be nice to see the performance of the options missing from this benchmark (autodefrag, inode_cache)
The comparison was very informative and useful, Michael.
However, an argument could be made that BTRFS lags behind EXT4 for the simple reason that the checksumming and healing power it offers is simply costing something. I think it would help the comparison a lot if Debian/kFreeBSD (or native FreeBSD) was installed in the same machine, and the benchmarks were run under ZFS, too.
That way, BTRFS would be compared to ZFS, which has similar features: checksums, snapshots, etc.
Just my 2c.
It shouldn't but it has plagued the Linux desktop for years (not that Windows fares much better though) even though it has been highly improved over the years, or I have simply bought better hw over the yearsCopying files shouldn't introduce latency in your desktop experience.
However I don't really think that we will find 100% of the problem in the kernel since I have never seen a server drop latency do to heavy I/O so perhaps our window managers access the disk more than they should and that is why is the cause of these latencies when there is high I/O. Or the I/O system gets completely clogged up so there can be no I/O over for keyboard and mouse (they are I/O operations as well).
And this not that far fetched since we all remember the Firefox + ext3 fsync fiasco. Who would think before that that Firefox would have latencies due to disk activity...
The supposedly superior EXT4 does not have encryption nor compression. NTFS-3G is not the same as NTFS-W7, but BTRFS is, with compression, file-permissions, multiple-dates, & encryption.
Personally all my data & archive files are NTFS-W7 (which differs from previous versions of NTFS). Linux, which I use for most functions, most times, uses EXT4 partitions, but creates many incompatibilities with NTFS-W7: non-MS file names, multiple same-name files & seemingly rare & random write errors onto compressed NTFS-W7 partitions.
Compression, presumably, would've forced more changes than T'so liked, and encryption is handled by a lower level system (in the nix tradition of "small" programs doing "small" tasks) that any fs (saving btrfs, at least) can take advantage of.