Our conversation got me interested again, so set up the share using nfs and did some playing. First repeated the problem. Yep still there. Then instead of rsync used simple cp. Same problem. So not application specific. Next checked into nfs.Ahhhh, I do believe I found the problem. I was using the safe 'sync' option in the exports file for the share. Changed to 'async' and now it flies. The processor usage for all four RPI cores actually can be pegged while receiving large files. Memory usage doesn't go up much at all. The downside of course is power failures that could corrupt the data. But battery backup and proper shutdown should solve that problem if I 'really' want to set the RPI4 up as a server. At least I know what now causes the slooooow down. Thanks for kicking me into gear to check into ths !

BTW, I use the 'sync' option on the tower server and all is well performance wise. The data is on new internal SATA SSDs as of a couple weeks ago. Even with the previous HDD, I didn't notice a significant slow down over nfs. Must be something to do with the USB 3.0 HDD drive or the USB controller on the RPI.

Even the NAS make little difference with Western Digital they have the WD Red NAS drive a SMR and then the WD Red Plus NAS a CMR. The weasels have put out a list on their website about which is which and it is in the description of the listing on places like amazon and newegg. They like to present it as out of the goodness of their heart but it is because of the law suits brought when people found out about the switch and sued. Oh the 6TB I use is SMR one of the ones in the hidden switch it was supposed to be CMR if they had kept their word on it. Christ I hate the scumbags in the computer industry the place is infested with them and has been since the beginning. I know I was there for all the garbage they have done. And hard drives being my pet peeve. In the start it was binary you got what the label listed for capacity now it is decimal, like my computer computes in decimal!, and the loss now with 10TB drives out there you get to see they have lied their way to an extra TB as the real capacity is 9TiB. That last one now I remember that lie with the abbreviations too.

They are not 'lying'. They are using advertising speak, since 10 TB sounds much larger than 9 Tib, even though the byte size is the same. My 3 TB WD drives actually give me 2.7 TiB so I have the same issue.

Almost all advertising is lying they are paid professionals at it. In legal terms it is called deception or fraud by misrepresentation. Somehow they get pass for it as they have bought the supposed standard bodies to have their scam method accepted as part of the standards. Sort of like the Chinese being part of the UN Human Rights body. They in no way support human rights and are there only to subvert the process.

Actually from what I read, when a manufacture markets the drive to us, they use 1000 bytes per KB (for the layman among us) rather than 1024 bytes per KB as the computer sees it. So a 500G drive is actually 465.66GB. Some space is also taken up by partitioning and formatting and such too.

Yeah the computer sees the binary it runs on. The 1024 the 1000 is a made up unit for the purpose of lies it is a decimal unit. Just where the hell is my decimal ram, the decimal programming they do not exist a computer is binary for all its workings hard drives included. They hijacked the standards body got their garbage passed into the standard so they could tell their lies. Plain and simple rather than do the decent thing and tell the hard drive manufacturers to stop their garbage they have all just let it continue. Even worse colluded with them in the deception, loaded with scummy weasels the computer business in a nutshell. The amount of things like this I have seen in my many decades of using these things is unbelievable at times. The technology companies have got too powerful, the effects on society are only beginning to be felt and a new dark age of repression is round the corner due to them. As those spineless politicians will do nothing to stop it, they will pass useless laws about anything else but protecting the people they are supposed to serve forget it, some filthy rich ahole might make a few dollars less. Not be able to kill off more people with their actions. After all unlimited growth and wealth accumulation has to preserved who cares how many die in the quest.

For a HappyTux, thou dost not sound very happy .

I've been 'satisfied' with my WD Red drives. Both times I had major problems with server drives over the years was with Seagate drives. So I've stuck with WD ... for now. Knock on wood. Rather than wait to go bad, after 3-4 years I swap out for a new one. With 4TB around $100, it isn't a big deal to do so. Things are a bit different now though as my server has three SSDs and the one backup 4TB HDD. 1 SSD for the OS, and 2 2TB SSDs for data. See how this behaves in the long term! I don't write much, so I 'think' they should last quite awhile. We'll see. No worry as they are fully backed up.

This is from my 3 TB drive using smartctl. Saying it is 3 TB is NOT a lie. They say it is 3 TB and in fact the byte size is 3 TB.
I cannot help it if the user sees the size in a different unit (TiB) on his system and thinks he got cheated. Educate yourself on what units are used and where they are seen and quit whining that what is said is not what you heard.

Please be careful and use the units properly.
500 GB (powers of ten) is equal to 465.66 Gib (powers of 2). A little is lost in formatting, partitioning, etc, but saying that a 500 GB drive is actually 465.66 GB is not a correct statement since you used the units incorrectly. Improperly using units is what causes things like this discussion.