vik2or Posted January 29, 2020 Share Posted January 29, 2020 (edited) I noticed that docker containers were slow on writing to mapped volumes, the dd inside the docker was 20x faster. First i thought it was something wrong with docker but then i did a dd test on the server root@Tower:/mnt# dd if=/dev/zero of=/mnt/disk4/DST/test.dat bs=1024 count=100000 100000+0 records in 100000+0 records out 102400000 bytes (102 MB, 98 MiB) copied, 0.182794 s, 560 MB/s root@Tower:/mnt# dd if=/dev/zero of=/mnt/cache/DST/test.dat bs=1024 count=100000 100000+0 records in 100000+0 records out 102400000 bytes (102 MB, 98 MiB) copied, 0.442347 s, 231 MB/s root@Tower:/mnt# dd if=/dev/zero of=/mnt/user/DST/test.dat bs=1024 count=100000 100000+0 records in 100000+0 records out 102400000 bytes (102 MB, 98 MiB) copied, 7.74579 s, 13.2 MB/s root@Tower:/mnt# dd if=/mnt/disk4/DST/test.dat of=/dev/null bs=1024 100000+0 records in 100000+0 records out 102400000 bytes (102 MB, 98 MiB) copied, 0.0804936 s, 1.3 GB/s root@Tower:/mnt# dd if=/mnt/cache/DST/test.dat of=/dev/null bs=1024 100000+0 records in 100000+0 records out 102400000 bytes (102 MB, 98 MiB) copied, 0.0693544 s, 1.5 GB/s root@Tower:/mnt# dd if=/mnt/user/DST/test.dat of=/dev/null bs=1024 100000+0 records in 100000+0 records out 102400000 bytes (102 MB, 98 MiB) copied, 2.76295 s, 37.1 MB/s I have an old KINGSTONE savage SSD as cache and form these test it looks that it has slower write speed than a hdd, i can live with that, but the /mnt/user speed is extremely slow. I saw that there are other topics that complain that they have slow speeds in /mnt/user but it was at most 50% slower not like this. Can anyone help with this? Edited January 29, 2020 by vik2or Quote Link to comment
vik2or Posted January 29, 2020 Author Share Posted January 29, 2020 Here is the diag data tower-diagnostics-20200129-1733.zip Quote Link to comment
testdasi Posted January 29, 2020 Share Posted January 29, 2020 Your test is heavily flawed. /mnt/disk4/DST/test.dat and /mnt/cache/DST/test.dat are duplicated files under /mnt/user/DST/test.dat. You then do an additional write test to /mnt/user/DST/test.dat. You just introduced an unrealistic variable to the test. You haven't made any attempt to remove the effect of RAM cache from the test. There is no SATA SSD / HDD that is capable of 1.3GB/s and 1.4GB/s read speed. Block size of 1k (1024) is equivalent to random IO. 100k of 1k files write to a parity-protected array at 13.2MB/s is completely NOT unreasonable. Let's simplify the test. Take 3 large (multiple GB) files, copy them using cp command and then watch the speed reported on the Unraid Main page of the GUI. Quote Link to comment
vik2or Posted January 29, 2020 Author Share Posted January 29, 2020 Ok, copying 2Gb+ files to hdd i get around 55MB/s and to ssd cache, 230MB/s and copying to /mnt/user i get similar numbers (if is no cache or cache preferd ). So i was just fooling myself into thinking i had a problem but i was using dd incorrectly. Quote Link to comment
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