Recent Wildly Fluctuating Copy Speeds of Large Files (125+ GB) to External Hard Drives

@Winuser ,

Thank you for sharing your experience. I still have the same issue. Like you, I think it is some kind of Windows bug that has decided to afflict my Dell 8930 SE. The overall copy speed, despite the fluctuations showing, is where it should be: 100 to 107 MB/s, according to the Teracopy Log.

I have decided to just ignore this copy speed display "glitch." It is simply a nuisance at this point.

Have a great day.

Regards,
Phil

I have a new home built desktop with a similar problem. (12 gen i5 CPU, 32G Ram)
I am trying to copy from an old internal SATA HDD to M.2 SSD. And the transfer is going painfully slow.

I have tried a number of different things, from Disabling the Indexing service, to running the command "netsh int tcp set global autotuninglevel=disabled" and unchecking Remove Differential Compression. None of which has helped. There is no third party virus software. This is a fresh install of Windows 11 Home.

I've also tried using Robocopy rather than file explorer.

What I have discovered after watching this for a few hours is that it will copy 10-15 mb of data very quickly, then it will pause for 10 seconds and do nothing, then it copies another chuck of the files and so on.

Any idea what is causing it to pause like this?

@edfiero As per our discussion over at answers.microsoft.com, have you tried Safe Mode?

LesFerch said:

@edfiero As per our discussion over at answers.microsoft.com, have you tried Safe Mode?

Click to expand...

Yes ,Thanks. Tried Safemode. No improvement.

edfiero said:

Yes ,Thanks. Tried Safemode. No improvement.

Click to expand...

You may have a hardware or driver problem. It may take some trial and error testing to isolate the issue with everything non-essential disconnected. But first, have you updated your computer's firmware?

Or it may be no problem at all.

My sister recently built a new desktop rig to replace her laptop. When we copied a bunch of old Macrium Backups from an older 4 TB Seagate desktop external drive to a brand new LaCie Desktop external drive, she experienced the exact same thing - and this was on a brand new install of Windows 11.

That was last week - yesterday, I was at her home when she had an issue with a very large folder of movies she had RIPped from her DVDs - and I watched it do exactly as what the OP describes with my own eyes. With some files it would drop from ~200 MB/s down to ~120 MB/s, but with other files it would drop flat to zero, and stay there for a second or two (and in a couple of cases, noticeably longer), but the overall transfer rate was within the spec of the drive over a USB 3.1 gen 2 Type-C connection to the LaCie.

So, twice on a system built at the beginning of this month.

johnlgalt said:

Or it may be no problem at all.
external drive to a brand new LaCie Desktop external drive, she experienced the exact same thing - and this was on a brand new install of Windows 11.
but the overall transfer rate was within the spec of the drive over a USB 3.1 gen 2 Type-C connection to the LaCie.

So, twice on a system built at the beginning of this month.

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In my situation I am working with an internal drive. So USB is not involved.

In my case it does seem to be a hardware problem. Although CHKDSK found no problems with the drive, other disc programs like HDSENTINEL identified there to be a communication issue between the drive and the motherboard. However I am at a loss; I switched to a different SATA cable, and a different port on the board, but the problem remained. I moved the drive back to the previous 8 year old computer and it works fine.

Was the drive on the old system encrypted using BitLocker or anything else? Is the new drive on your new system encrypted with BitLocker?

Yes, I've had the fast/slow/fast copy issue with Win11 on copying large map/data files (~200Gb) to external USB disks for backup safety.

I tested this with two different laptops - same files and external disks - and found the same issue. All I could find in the MS literature was a brief acknowledgement of this issue accompanied with the escape clause about "most home users won't need to experience this" (which assumes that most do not have large files to copy). So I tentatively concluded that this was a RAM management issue with Win11 that MS had no intention of resolving as yet.

My own resolution for this was to sort out some batch files using RoboCopy. Seems to work as a sync tactic, with copy progress quite fast and without any significant fluctuation.

ian50 said:

So I tentatively concluded that this was a RAM management issue with Win11 that MS had no intention of resolving as yet.

Click to expand...

That's an interesting take on it.

Perhaps that is one of the reasons why I simply don't see it as much.

Which, when tied in with the OP's analysis, as well as several other posters with similar issue, might, in fact, be a bit larger than this - not just a RAM mgmt issue, but also much larger, and much faster, data transfer caches (write buffers), that the system is able to fill up much more easily, than the drive(s) can actually keep up with.

The running theme here seems to be that older (and usually mechanical) drives work fine in / with older systems, but seem to do this stop-and-go process on newer systems. My own system has no mechanical drives in it, and has gobs of RAM, so the SSDs play nicely with my file transfers - even when transferring hundreds of GBs.

But even on an internal architecture, like SATA, older drives simply may not have a sustained write capability to keep up with how fast a newer machine can fill write buffers, so there is a necessary pause to let the drive(s) in question play 'catch up', or more technically speaking, give it enough time to flush the buffers after writing the data to disk so it can accept more data.