Finder + NAS + copy = broken?

[Basic75]

So I have a regular Synology NAS used with SMB, and it all works well except for one thing that has been an annoyance for years.

A small copy from or to the NAS using the Finder works, but when it's a larger copy then the operation will usually fail at some point.

When I do an equally large or even larger copy with rsync in the Terminal it always succeeds, network and network filesystem are good.

Anybody else have the same problem? Any ideas on how to make Finder more reliable with network filesystems?

 

[Slartibart]

we need more details here: what version of macOS on what Mac model, which version of Synology`s DSM?

 

[Bigwaff]

Along @Slartibart line of questioning… need network info… wired or wireless network? Wireless router/switch details?

 

[Basic75]

All kinds of macOS versions across a few years, most recently Tahoe 26.3.1. An M1 Mac mini and an M1 Max MacBook Pro. Whatever the latest DSM version was over the last years, most recently DSM 7.1.1-42962 Update 9. Both with wireless and wired network in three completely different setups. I don't see how the network or even SMB can be the problem when rsync works just fine, and that's rsync running locally on an SMB mounted volume, while the Finder often doesn't.

 

[Bigwaff]

Do you use the Synology for Time Machine backups? Network TM is over SMB.

 

[Basic75]

Do you use the Synology for Time Machine backups? Network TM is over SMB.

No.

 

[Slartibart]

All kinds of macOS versions across a few years, most recently Tahoe 26.3.1. An M1 Mac mini and an M1 Max MacBook Pro. Whatever the latest DSM version was over the last years, most recently DSM 7.1.1-42962 Update 9. Both with wireless and wired network in three completely different setups. I don't see how the network or even SMB can be the problem when rsync works just fine, and that's rsync running locally on an SMB mounted volume, while the Finder often doesn't.

Your DSM version is a bit ”away” from more current ones - the latest is DSM is 7.3.2-86009. I strongly recommend to update. Check the DSM SMB settings:

and check the MTU size settings on your Mac(s) - try e.g. ”1496”.

What does your router or the macOS console logs tell when smb transfer stall?

 

[Basic75]

Your DSM version is a bit ”away” from more current ones - the latest is DSM is 7.3.2-86009. I strongly recommend to update.

It says that the version I have is "up to date". I will udpate the advanced SMB settings as per your suggestion and see whether that helps. I'll also check the MTU though I can't imagine how that can be the culprit, not with rsync, and cp, working perfectly. Thanks.

 

[Slartibart]

It says that the version I have is "up to date". I will udpate the advanced SMB settings as per your suggestion and see whether that helps. I'll also check the MTU though I can't imagine how that can be the culprit, not with rsync, and cp, working perfectly. Thanks.

In the DSM network settings under »Edit«. verify that iP6 is off. depending on your router that might causing the problem.

 

[cjsuk]

This doesn't surprise me. I have the same issues sometimes.

It's not MTU or network related - it's finder bugs. Finder doesn't just copy files verbatim. It creates placeholders in the destination and spews a load of metadata over. Then copies the files. That gives it the "resumable" copy thing and checks that the destination volume has enough space and reserves it, which sort of breaks everything even worse than the problems it is trying to solve.

I just use cp/rsync now for that stuff!

 

[Brian33]

A small copy from or to the NAS using the Finder works, but when it's a larger copy then the operation will usually fail at some point.

When I do an equally large or even larger copy with rsync in the Terminal it always succeeds, network and network filesystem are good.

My understanding is that rsync (when you specify a remote destination on the rsync command) never uses the SMB protocol. It has its own network protocol. It never connects to the SMB server on the remote end. Instead, it can connect to a rsync daemon on the remote end, if it exists, or it can fork the remote shell process to create its own rsync server on the remote system. I think this latter method is the more common situation.

Thus it makes sense that certain bugs or problems could affect SMB transfers and not rsync transfers.

I think the situation indicates that the problem is with the SMB client, the SMB server, or the associated settings. However, @cjsuk makes a good point. It could be a finder issue and not an SMB issue. Have you tried using Finder to mount the remote share, and using ‘cp’ in the terminal to copy the same data to the local mount point? That should use SMB. If it worked, to me that indicates the problem is likely in Finder. If it fails similar to your big Finder copies, to me that indicates an SMB problem.

 

[Basic75]

My understanding is that rsync (when you specify a remote destination on the rsync command) never uses the SMB protocol.

That's not how I'm using it. The NAS is mounted into the Mac with SMB and rsync operates on that.

 

[Bigwaff]

Hmm.. so you are using rsync (remote sync) to sync files between locally mounted directories, one being a remote directory mounted using SMB. Why not skip the middle man?

 

[chown33]

That's not how I'm using it. The NAS is mounted into the Mac with SMB and rsync operates on that.

I think rsync will verify data after writing, so maybe that's a factor.

I second the above suggestion about using 'cp' to see if it works or fails. AFAIK it doesn't do any verification, but just does plain block reads and writes. Or maybe just 'cat' with a redirected output stream.

The 'dd' tool might be another thing to test. I know you can tell it to use specific buffer sizes, but it's mainly working with a single input and a single output. Still, if it works with certain buffer sizes and fails with others, that might be informative.

Also, how are the various devices connected to the network? Are there hubs or switches involved? Is one on ethernet and the other on wifi? Which wifi band? What ethernet devices, cables, etc.? Router model? Jumbo packets? What if you do a direct Mac-to-NAS connection with a single ethernet cable?

 

[Basic75]

Thank you for all the suggestions, I'll be testing for a while.

Hmm.. so you are using rsync (remote sync) to sync files between locally mounted directories, one being a remote directory mounted using SMB. Why not skip the middle man?

It works.