Recording stops with incorrect disk space warning

[yoshihito-saito]

Hello,

I am experiencing an issue with Open Ephys during recording.
The recording starts normally, but after a few minutes it sometimes stops with the following warning message:
“Recording stopped. Less than 5 minutes of disk space remaining.”
However, the drive I am using has more than 2 TB of free space available.
One additional detail is that I am not recording any neural activity signals at all. I am only recording ADC data.
Also, after this warning appeared and the recording stopped, I started recording again and was able to continue for more than 30 minutes without any issue.
This problem did not occur at all until yesterday. Starting today, however, the same issue has happened 4–5 times.
I would appreciate any advice on what might be causing this problem and what I should check or change to troubleshoot it.

GUI version: v1.0.2
OS: Windows 11
Electrode type: Not applicable, since I am not recording neural signals and am only recording ADC data

Thank you.

[anjaldoshi]

Hi @yoshihito-saito,

This sounds similar to issue #687

The Record Node’s disk-space check estimates the remaining recording time from the current data rate and available free space. If the data rate changes during recording, that estimate can become more conservative and may trigger the low-space warning earlier than expected.

A few things to check:

• Watch disk usage while recording in Windows Task Manager’s Performance tab.
• See whether the recording rate is fluctuating a lot during the session.
• Since this only started appearing today, consider whether anything in your setup recently changed, such as a new external data source like a camera writing to the same drive.
• If nothing changed on your side, it could also be worth considering background OS activity, such as Windows Update or file indexing, affecting disk performance.

[yoshihito-saito]

Hi,

Thanks for your suggestions!

I did some additional testing and found that the issue seems to occur when recording together with a camera. However, this setup (recording together with the camera) has been working without any issues until yesterday.

Also, I checked my system and found that Windows updates were installed on April 13, which matches the timing of when this issue started appearing (the problem began on April 14). This is the only recent system change I can identify.

Is there any way to disable or adjust the low disk space check in the Record Node? Alternatively, is there a way to make the estimation less conservative?

Thank you.

[anjaldoshi]

Thanks for providing the additional details.

Since the “Less than 5 minutes” check is based on a dynamic but unsmoothed, instantaneous data rate estimate, it can result in intermittent false positives. An OS level write back cache flush can cause a temporary spike in the observed consumption rate within a given five second window. This yields a transiently high data rate and can incorrectly stop a recording that would otherwise have had plenty of time remaining.

In your case, because camera data is also being written to the same drive, the OS may be caching significantly more Open Ephys data in RAM before flushing it to disk intermittently. This can further amplify these short lived spikes and lead to false positives. I am not sure why this started happening all of a sudden, or whether it is related to a recent Windows update.

I made an attempt to address this by applying an exponential moving average to the data rate calculation used by the Record Node disk space checker, which smooths the estimate. I built new GUI binaries with this fix applied and have attached them here.

open-ephys-v1.0.2-disk-space-checker-fix-windows.zip

If you are able to try this version and let me know whether it resolves the issue, that would be great. You can simply extract the zip file and run the GUI directly from the extracted folder. This will not overwrite your existing installation, and it will continue to use the same plugins you already have installed.

Let me know how it goes.

[yoshihito-saito]

Thanks for the explanation and the patched version.

I tested it, and it seems to resolve the issue. I was able to record with the camera running without triggering the warning.

Thank you!

[anjaldoshi]

Thanks for confirming that the fix is working. I will merge it into the development branch, and it will be available in the next GUI release very soon. I will close this issue after the release is out.