Linux is running great, but it's limited on read/write speed. Seems both HDD are limited to ~30MB/s when using basic tools (and so is flash drive). NFS is limited to 30MB/s. cp is limited to 30 MB/s. pv is limited to 50MB/s. dd is slow as well (unless we use oflag=direct!)
However hdparm is much faster, the only tool that gives real speeds (alongside dd oflag=direct)
(dmesg is large and is attached).
htop with kernel threads shows a lot of cpu spent in kworker/u4:2-events_unbound or kworker/u4:1+flush-8.16 (see attachment). However I can't tell if it's real CPU load or just CPU waiting for IO.
However hdparm is much faster, the only tool that gives real speeds (alongside dd oflag=direct)
(dmesg is large and is attached).
root@debian:~# uname -a Linux debian 6.14.6-kirkwood-tld-1 #1 PREEMPT Wed May 14 17:08:50 PDT 2025 armv5tel GNU/Linux root@debian:~# cat /etc/debian_version 12.2 root@debian:~# hdparm -Tt /dev/sda /dev/sda: Timing cached reads: 556 MB in 2.00 seconds = 277.36 MB/sec Timing buffered disk reads: 374 MB in 3.00 seconds = 124.50 MB/sec root@debian:~# dd if=/dev/zero of=/dev/sda bs=10M count=100 oflag=direct 100+0 records in 100+0 records out 1048576000 bytes (1.0 GB, 1000 MiB) copied, 8.14149 s, 129 MB/s root@debian:~# dd if=/dev/zero of=/dev/sdb bs=20M 93734+0 records in 93734+0 records out 1965744455680 bytes (2.0 TB, 1.8 TiB) copied, 54092.5 s, 36.3 MB/s <no new dmesg messages>
htop with kernel threads shows a lot of cpu spent in kworker/u4:2-events_unbound or kworker/u4:1+flush-8.16 (see attachment). However I can't tell if it's real CPU load or just CPU waiting for IO.