It looks like zfs-fuse will update the compressratio data every 30 seconds with limited IO occurring but there is another trigger to the update as background IO or really large files cause the data update to occur sooner.
I've put some test functions up on a gist. They require a clean (no files) file system that will start at 1.00x.
If the scripts pause forever on the first test then your compression counters are never updating and you have an issue with your install.
Running the scripts on a Debian wheezy box:
$ uname -a Linux zfs-fuse 3.2.0-4-686-pae #1 SMP Debian 3.2.54-2 i686 GNU/Linux
Results in the following:
$ test_compression compress Testing [compress] Testing size [4096] Waited 0 seconds for [compressratio_is_one] 4096 bytes made up of 1*4096 blocks Waited 20 seconds for [compresstario_is_not_one] 1.12x Testing size [16384] Waited 30 seconds for [compressratio_is_one] 16384 bytes made up of 1*16384 blocks Waited 30 seconds for [compresstario_is_not_one] 1.53x Testing size [1048576] Waited 30 seconds for [compressratio_is_one] 1048576 bytes made up of 1*131072 blocks Waited 30 seconds for [compresstario_is_not_one] 31.44x Testing size [33161216] Waited 30 seconds for [compressratio_is_one] 33161216 bytes made up of 255*131072 blocks Waited 0 seconds for [compresstario_is_not_one] 202.31x
You can reduce this, normally by about half by doing something intensive in the background which probably triggers the counter update.
In the background
$ while true; do touch somefile; rm somefile; done
Then testing again:
$ test_compression compress Testing [compress] Testing size [4096] Waited 0 seconds for [compressratio_is_one] 4096 bytes made up of 1*4096 blocks Waited 5 seconds for [compresstario_is_not_one] 1.11x Testing size [16384] Waited 17 seconds for [compressratio_is_one] 16384 bytes made up of 1*16384 blocks Waited 17 seconds for [compresstario_is_not_one] 1.50x Testing size [1048576] Waited 16 seconds for [compressratio_is_one] 1048576 bytes made up of 1*131072 blocks Waited 10 seconds for [compresstario_is_not_one] 29.73x Testing size [33161216] Waited 0 seconds for [compressratio_is_one] 33161216 bytes made up of 244*131072 blocks Waited 0 seconds for [compresstario_is_not_one] 201.35x
Of note, on FreeBSD the update happens ~ every 5 seconds:
$ test_compression giggidy/compress Testing [giggidy/compress] Testing size [4096] Waited 0 seconds for [compressratio_is_one] 4096 bytes made up of 1*4096 blocks Waited 4 seconds for [compresstario_is_not_one] 1.21x Testing size [16384] Waited 5 seconds for [compressratio_is_one] 16384 bytes made up of 1*16384 blocks Waited 5 seconds for [compresstario_is_not_one] 1.91x Testing size [1048576] Waited 5 seconds for [compressratio_is_one] 1048576 bytes made up of 1*131072 blocks Waited 5 seconds for [compresstario_is_not_one] 39.33x Testing size [33161216] Waited 5 seconds for [compressratio_is_one] 33161216 bytes made up of 1*131072 blocks Waited 4 seconds for [compresstario_is_not_one] 114.25x
I will add a Solaris based example when I can get on a box.
