I'm running OpenWrt 19.07 on a MyBook Live device (thanks for supporting it) which has 800 MHz single core CPU, 256 MB of RAM and one 1GbE adapter.
The device itself is a NAS so not the typical OpenWrt use case, but it is supported and thanks to the outline of a user of the community, I'm making my way through having a fully operational NAS again.
So far I've managed to get a working system with partitions mounted and also managed to configure smartd for hard drive health monitoring. The hard drive itself is a brand new WD Red 4 TB.
After installing and configuring Samba 4, I get slow write speeds: up to 80 Mbps, while read speeds are around 190 Mbps. I've tried disabling async-io, read tops to 240 Mbps, but write remains the same. In order to exclude some kind of disk or system issue, I've tested write speeds on the NAS itself (classic
dd if=/dev/zero of=/mnt/ext4partition/somefile) and the results are around 75 MB/s, so the bottleneck is not there. During write transfers CPU hardly exceeds 50% and a lot of RAM is cached (upper row in
top); when no more memory is free (though available) for caching, transfers get a little slower, but not significantly.
I would like to further investigate the issue, but don't know how. Is this a known problem with Samba 4? Is there any solution?