Solved: Slow disk writes

[jogger]

I was experiencing slow writes to internal SD card and hard drives connected to an USB 2.0 hub on multiple Odroid HC1. IOWAIT was 99.99% most of the time during large file copies.

I found that Armbian was simply waiting too long to write data to disk. Kernel parameters are optimized for writing small amounts of data to SD card when running from that in order to reduce wear.

If you have the same problem, you might get factor 10-100 faster writes using the following sysctl settings:

vm.dirty_writeback_centisecs=50
vm.dirty_expire_centisecs=50

No need to act, if iotop shows low IOWAIT values on your system.