Copying a large amount of files (around 100 000 ; 500 Gb) from 2 NAS using Windows Explorer, i got :
- very slow response time after une hour of copy (50 Mb to less than 1 Mb)
- high memory consumption on freeNas server
If I cancel the transfer, memory seems not to be flushed on the server and the system is globally slow. I solved this with a reboot.
- Status changed from Unscreened to Closed
- Target version changed from Backlog to N/A
- Reason for Closing set to User Configuration Error
- Needs QA changed from Yes to No
- Needs Doc changed from Yes to No
- Needs Merging changed from Yes to No
As I see, at the time of the debug taken several of your pools has been scrubbed. Considering those are single disk pools, it is not very surprising that it affected performance. I don't know your motivation, but instead of 6 separate one-disk pools you should better create one or few pools of few disks. It would give you better performance and maybe, depending on used layout, reliability.
Also I see that your SATA controller is configured for legacy (not AHCI) mode, that means lack of NCQ, i.e. that each disk can execute only one command at a time. Also 4 of your disks share 2 virtual legacy ATA ports, and so also can't work simultaneously.
What's about memory consumption, I see nothing interesting -- all memory available in system must be used for top efficiency, so unless you have excessive swapping or application errors, there is no problem.