We use the AudioMoth with large batteries for long term bat monitoring. Our normal standard is 5 sec. recording 10 sec. pause. After some days the writing on the SD card is running slow. Typical after there is 35,000 files on the SD card. The result is that only every second files is saved. (Turn into 5 sec recording 25 sec pause). After 70,000 files is on the SD card the writing becomes even slower and the only every third or fourth file is saved. Batteries are ok, and there are plenty of space on the 128 Gb SD card. Interestingly the problems can be solved if we manually transfer the 35,000 files to a separate folder on the same SD card. It could be great if the setting could allow a daily folder or any other suggestion to solve the problem.
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Large number of files make the writing on the SD card slow
Large number of files make the writing on the SD card slow
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Great news. Thanks for the very efficient support. We will be very happy to test it. I will send you a mail with details.
The 'daily folder' option works well. The file opening delay is reset each day as a new folder is created. We've tested with writing 5 seconds files with 5 seconds of sleep between them, which is effectively the worst case. We're also updating the energy calculation to better reflect the energy consumption of opening each file. It is sometime better to record for longer to avoid generating so many files, and then having to take the energy penalty with the long period to open the file. This will be out in the next firmware and configuration app release in March. Let us know if you want a test release to try out.
Hi Alex, Ecellent. If you have any pre-version please let me know. We are working on several project of using AudioMoth for long term monitoring for bats, birds and whales. We successfully tested SD-card up to 512 Gb, using solar power and large batteries and developed an external weather proof microphone to be used in marine condition. Morten
Hi Morten, We're testing this now. Will let you know if this fixes it. Alex
Hi Alex, Thanks for the reply. If you do some coding for writing sub-directories we will be happy to test a first version. I will apply 15 modified AudioMoth on marine buoys in the Baltic Sea in March and need a setup for long-term use.
Hi Morten, Yes, writing lots of files will make it quite slow to open a new file as the AudioMoth has to read through the file allocation table to find space for the file. Eventually this may take long enough that the AudioMoth ends up skipping recordings to try to keep on schedule. You will also eventually reach the format limit of 64K files per directory if using FAT32 format. We'll do some experiments to see if writing to a sub-directory improves things. It may have done in your case as the AudioMoth then only needs to read the file allocation table for the main directory, once all the files are moved. We would need to write directly to a sub-directory and I'm not sure that it would yield the same improvement as the AudioMoth would still have to read a large allocation table to find space for the new file. Alex