Two NAS directly connected via LAN with slow transfer speed

[fabrizio.foresti]

Hi, I have two NAS:
1) QNAP TS-453D-8G with 4 x WD60EFAX 6Gbps HDs in RAID5 and SMB 2.1 configuration
2) QNAP TS-439-Pro II Plus with 4 WD30EZRX 6Gbps HDs in RAID5e SMB 3 configuration
I connected the 2 NAS directly with a CAT6 LAN cable without going through any router and I configured a one-way synchronization process on HBS3 of the TS-453D-8G with:
a) Speed limit 1000 MBps
b) BBR TCP congestion control
c) integrate with QuWAN
d) manual network interface (adapter 2 - direct cable) with Jumbo Frame 9000
Why is the transfer rate maxing out at 12-15 MBps?

I use the QNAP TS-439-Pro II Plus as folder access only, while I manage the HBS3 sync process from the QNAP TS-453D-8G.
Is there any way to connect them directly in some mode to speed up the data transfer?
The QNAP TS-439-Pro II Plus despite having SMB2.1, still has two 1Gbps interfaces so I would expect that with a direct connection between the QNAP TS-453D-8G and QNAP TS-439-Pro II Plus the systems would go much faster than 12 MBps.
I have read in some QNAP forums that the slowness was attributed to the type of HD WD60EFAX or WD30EZRX even if at 6 Gbps and in RAID5 mode.
Thank you

[fabrizio.foresti]

Excuse me ...
1) QNAP TS-453D-8G with 4 x WD60EFAX 6Gbps HDs in RAID5 and SMB 3 configuration
2) QNAP TS-439-Pro II Plus with 4 WD30EZRX 6Gbps HDs in RAID5e SMB 2.1 configuration
I inverted SMB configuration.
Sorry

[dolbyman]

The WD60EFAX were a bad buy...these are SMR disks..with slow prolonged write speeds and even kicked out disks during sustained writes..best to swap them (contact WD support for deceptive marketing..they will swap them with CMR drives)

The green drives in the other NAS are also not NAS rated but that was more due to excessive head parking.

[fabrizio.foresti]

Thanks @dolbyman, but is the low quality of the HDs the cause of the low lan transfer speed?

[beneix]

I have found the synchronisation to be demanding of the CPU on both of two machines in a similar scenario, so the ARM processor on the 439 may be the limiting factor.

[dolbyman]

The SMR drives can indeed cause low speeds

After prolonged writes or during a rebuild, they can be so low that drives might get kicked out of the array