Yet another update:
a) I've tried everything with me EX41-SSD server on Hetzner and nothing is increasing the performance over & above the default configuration.
b) I tried commissioning a new EX41-SSD server and was able to replicate the same pathetic performance numbers.
c) I tried another cloud hosting provider (E2E Networks) and just the raw performance numbers (with default configuration) are blowing Hetzner out of the water.
This leads me to believe that my assumption of the first hardware (or SSD) being faulty is incorrect. Something is wrong with either the EX41-SSD hardware or the out-of-box configuration. I'm commissioning something from their PX line (which is marked as "Datacenter Edition") and checking if that makes things better.
+--------+--------------+------------------+
| client | Hetzner | E2E Networks |
| | EX41-SSD [1] | Cloud Server [2] |
+--------+--------------+------------------+
| 1 | ~160 | ~400 |
+--------+--------------+------------------+
| 4 | ~460 | ~1450 |
+--------+--------------+------------------+
| 8 | ~850 | ~2600 |
+--------+--------------+------------------+
| 12 | ~1200 | ~4000 |
+--------+--------------+------------------+[1] lshw output for Hetzner - https://gist.github.com/saurabhnanda/613813d0d58fe1a406a8ce9b62ad10a9
[2] lshw output for E2E - https://gist.github.com/saurabhnanda/d276603990aa773269bad35f335344eb - since this is a cloud server low-level hardware info is not available. It's advertised as a 9vCPU + 30GB RAM + SSD cloud instance.
-- Saurabh.
