I have a 6 TB SATA HDD with the ext4 filesystem connected to Linksys EA8500 router by the eSATA interface.
I've tested HDD speed by dd, and obtained these results:
root@OpenWrt:~# time dd if=/dev/zero of=/mnt/D/test1.img bs=100M count=128 128+0 records in 128+0 records out real 1m 53.52s user 0m 0.01s sys 1m 43.84s root@OpenWrt:~# time dd if=/mnt/D/test1.img of=/dev/null bs=100M count=128 128+0 records in 128+0 records out real 1m 20.85s user 0m 0.00s sys 0m 40.51s
After calculations, I've obtained a write speed of 112 MB/s and a read speed of 158 MB/s which is OK for this HDD.
But the speed of reading and writing files by the FTP protocol (vsftpd server) and SMB (ksmbd) are much lower:
FTP: read speed 30 MB/s, write speed 58 MB/s.
SMB: read speed 28 MB/s, write speed 55 MB/s.
From output of top: near 49% sys load, near 20% sirq load.
Why such a drop in speed occurs? Is my router's 2-cores CPU by 1.4 GHz each (IPQ8064) is to slow for quick FTP or SMB transfers?