Slow transferspeed with sshfs + osxfuse version > 2.8.3

[ibaun]

Mounting a network disk with sshfs on macosx seems to give me very slow transfer speeds.

Test setup:

• Ubuntu server 16.04 on remote end
• mac osx 10.11.6 on local end
• sshfs remote@ip:. ~/dir
• rsync --progress ~/dir/somefile ~/

With a direct scp remote@ip:dir/somefile ~/ I get about 110 MB/s transfer speed.
Using sshfs over osxfuse, the results are:
rsync from sshfs 2.9.0 + osxfuse 2.8.1: ± 55 MB/s
rsync from sshfs 2.9.0 + osxfuse 2.8.2 & 2.8.3: ± 50 MB/s
rsync from sshfs 2.9.0 + osxfuse >= 3.0.4: ± 10 MB/s

This has been discussed also at libfuse/sshfs#11, with the latest results pointing more towards a problem with osxfuse than sshfs.

[bfleischer]

The slow transfer speeds are a result of an incompatibility between sshfs and FUSE for macOS 3.x. sshfs returns "wrong" values in sshfs_getattr() and sshfs_fgetattr().

The st_blksize value of struct stat represents the optimal block size for file I/O operations. FUSE for macOS will use this value when performing read or write operations on the file. The smaller st_blksize is the more context switches are required to complete the operation.

Setting st_blksize to 0 results in FUSE for macOS falling back to the global I/O size, that can be specified through the -o iosize=... mount-time option.