File transfers stop every 5 seconds

When I copy a file from my PC (typically the source is a 970 Pro 1TB), to an internal disk on my file server over my 10Gbit network it starts at 1.1GB/s then drops to zero, where it stays for 20-30 seconds, then goes back up to 1.10GB/s for 2-3 seconds, then drops to 0 again. This repeats until the file is copied.

If I copy the file to a drive attached to the server via USB I get a solid 220 - 240MB/s

I upgraded to Windows Server 2019 (1809), from Windows Server 2012 R2. There was a reason, apart from 2012 R2 mainstream support ending in 2018, something wasn't compatible... I just don't recall what that was.

On 2012 R2 copies would vary between 800 - 1100MB/s but would never stop

I also installed a new 12TB drive around the same time.

So, without going back to Server 2012 R2 to prove it, I don;t what else to do.

The drives are either ST10000VN0022 (x6), or ST12000VN0008 (x5). Network is all 10Gbit.

My gut tells me it sounds like a caching issue, but caching is enabled on all drives.

Before I go spend a day re-installing 2012 R2 to prove if that's the cause, any one have any other ideas what might cause this behavior across all internal disks?

EDIT: I've run chkdsk and defrag over all drives.

The source is a fast 970 Pro drive, the 10Gbit network is also fast (are you sure it's 10 G?) but the target is a slow HDD.
Despite the SATA 600, never seen a HDD that is faster than 150 MB/s or 1200 Mb/s.

"It starts at 1.1GB/s then drops to zero, where it stays for 20-30 seconds, then goes back up to 1.10GB/s for 2-3 seconds, then drops to 0 again. This repeats until the file is copied."
This behavior is explained as it loads the disk cache (RAM) very fast (for 2-3 seconds) and then writes to the disk from the cache very slowly.

If you copy the file to a drive attached to the server via USB you get a solid 220 - 240Mb/s (bits not byts). In this case the bottle neck is the USB, not the disk.

Thanks for your reply.

When I say MB/s I mean MEGABYTES per second. Not bits.

Yes, I am sure my network is 10G. The NICs are 10G. The cables are Cat6, the switches are 10G Netgear MS510-TX. Network properties shows the NICs at both ends running at 10G. RSC has been disabled at both ends, which according to Netgear is supposed to stop erractive transfer speeds, and Fast connect is also enabled on the switch ports.

But bear in mind, before upgrading Windows Server and upgrading a drive, this all worked fine.

On a gigabit network, best transfer speeds are 113MB/s regardless of the source or target device, and regardless of the target being internal or external.

The External USB drive is a USB 3.2/3.1 Gen 2 over USB Type-C that runs at Max theoretical of 20Gb/s (bits). That is why I get 240MB/s (bytes) sustained transfer speed. That's twice the gigabit link performance, and since low usage stuff and backups are on the external drive, I'm fine with only doubling my transfer speed there. It's the internal drive speeds that no longer performing

When copying to the internal drives on Windows 2012 R2 I was getting speeds of 800MB/s - 1100MB/s (bytes). I upgraded to Windows Server 2019, and also upgraded one drive and the speeds are now 1100MB/s (bytes) for 3 seconds, 0B/s (bytes) for 20 - 30 seconds, then 1100MB/s (bytes) for another 3 seconds etc.

Even with write caching enabled on the drives this behavior is the same.

The theoretical max sustained write speed on the NAS drives is 210MB/s (bytes) with a 256MB cache.
https://www.seagate.com/www-content/...04GB-en_AU.pdf

I timed a transfer of a 50GB file. Averaging the speed over the total time, I managed to get an average transfer speed of 40MB/s, that's one third of the sustained speed of a gigabit link.

I don't recall the reasons why I felt compelled to upgrade to Server 2019. I guess I'll be reminded as soon as I go back to 2012 R2, which it looks like I'm going to have to do. WSUS is broken on 2019 anyway, so I'll possibly fix two issues by reverting.

Don't think that the server version is the problem.
As I wrote before, never seen a HDD with transfer speeds higher than 150 MB/s so I doubt you have a HDD capable of 800MB/s - 1100MB/s.
A USB3.2 / 3.1 can have a high transfer rate but, again, the bottle neck will be the HDD.
The whole picture seems to be unreal.

Megahertz said:

Don't think that the server version is the problem.
As I wrote before, never seen a HDD with transfer speeds higher than 150 MB/s so I doubt you have a HDD capable of 800MB/s - 1100MB/s.
A USB3.2 / 3.1 can have a high transfer rate but, again, the bottle neck will be the HDD.
The whole picture seems to be unreal.

I'm pretty sure I'm not suffering from hallucinations. Once I've gone back to 2012 R2 I'll take some pics. But for now, here's some of the server copy and to/from USB. The server copy on 2012 R2 was not this bad - sure there was some fluctuations in speed, but not grinding to a complete halt.

I know what's happening - it's filling the cache and waiting for the write to finish then starting again. But this was not an issue on 2012 R2. Maybe it's the specific drive failing? I'll run Seagate's Seatool's across the drives and see what that says.

Problem solved.

The reason I upgraded to server 2019 was because the OpenVPN TAP adapter would not install on Win 2012 R2. Fortunately, OpenVPN developers released a fix on April 17th 2020, which resolves that problem.

My file transfers are now more stable (600 - 1100MB/s) and WSUS works like it should.

All by reverting to Win 2012 R2.