Unable to compare due to "stream read error"

[Per]

I am trying to do a file compare between two locations. I repeatedly get the error message
"Unable to compare XXX.XXX: Stream read error"
(xxx.xxx is various file names, all are image files)

What does this mean, what's the problem? And more importantly, what is the cure?

It is not systematic, i.e. it does not happen all the time. But quite frequently.

Context:
Win 7
BC 4.0.7 (19761)

Compare location 1: a folder on a local NAS server
Compare location 2: Amazon Cloud Drive mapped as a local drive as Z: using ExpanDrive

Both locations are accessible through Windows explorer. There are no network issues.

[Aaron]

Hello,

Beyond Compare generally stresses locations more than Explorer, since we are loading all items in all subfolders at once, where Explorer only needs to list the visible folder. One of the two locations is probably hitting this error due to this.

Are there any updates available for the NAS device or ExpanDrive?

If you compare NAS to a temp directory on your Desktop, do you hit the error?
If you compare ExpanDrive to a temp directory on your Desktop, do you hit the error?
This would help us narrow down which remote location is causing the problem.

[Per]

Aaron,

Don't think it is the NAS that is the problem, more likely the Expandrive.

I frequently do compares between the NAS and an attached USB drive and never have any problems.

But what do you mean with

we are loading all items in all subfolders at once

?

You can't possibly mean that all items to be compared are loaded into a local folder?

When I do compares between the NAS and the attached USB drive it can be many tens of thousands of files (terabyte) and it works fine. It could not possibly all be loaded all at once into a temporary local folder.

So:

Are there any updates available for the NAS device or ExpanDrive?

No, all up to date.

If you compare NAS to a temp directory on your Desktop, do you hit the error?

Cf the USB drive compare. It works fine.

If you compare ExpanDrive to a temp directory on your Desktop, do you hit the error?

Have not tried, but the way it works when comparing the NAS to the ExpanDrive is that most compares work fine but some don't. So if I tried on a desktop folder it would most likely be the same. It is not a systematic error. And it is not necessarily the same files that cause error if I try again.

But what does the error message mean

Stream read error

? Does it mean that BC could not read the drive/file ?

[Aaron]

Hello,

Right, stream read error is usually a transitory error attempting to access the file but the device returns the error instead. If you've already tested NAS to a USB drive with no errors, that does point at ExpanDrive as the issue.

We are loading the entire directory structure to look at/scan all files in subfolders, while Explorer only lists the files in the currently viewed folder. Clicking on a subfolder then expands it and lists its contents. It isn't downloading all of the file, but it is asking for directory listings to perform the default comparison of timestamp and size. A content scan would download temporary files in order to run the content scan, but then deletes each temp file as the comparison for them finishes.

If you load smaller subfolders as the base folders, or disable auto scanning (Session Settings, Handling tab) and then use the right-click Open and Open Subfolders command (to limit the number of items loading at once), does this have an impact on how often the error is hit?

[Per]

If you load smaller subfolders as the base folders, or disable auto scanning (Session Settings, Handling tab) and then use the right-click Open and Open Subfolders command (to limit the number of items loading at once), does this have an impact on how often the error is hit?

That's difficult to say. I have tried to compare just small folder (<100 files) and mostly it works fine. But sometimes not. Again, not systematic errors. And a folder that gave an error one time may scan OK another time.

I will do a test to see if it makes any difference if I only compare file size. By default it seems BC compares file size and time stamp. That in itself is a problem since on Amazon Cloud Drive the time stamp seem to be the time the file was uploaded to Cloud Drive and thus always different to the time stamp on the NAS drive.

This meant that all files were reported as different. And thus the only way to check if the NAS files were the same as the Cloud Drive files was to do a file compare.

But I now found the setting in Session Settings that allows me to compare only the file size.

[Aaron]

Disabling timestamp will probably not help with this error, but could improve the comparison if it is inaccurate because the timestamp is always different. However, please note that files can be edited but retain the same size; you would want to keep this in mind when comparing your files. Occasionally, you could use a full content scan (Binary, for example) to check file content to see if files are exact copies of each other. This would take significantly longer, as it does require download the files temporarily to perform the scan.