Read/write cycle while uploading normal?

Hello everyone

I’m currently using Nextcloud 13. Being a complete beginner, I followed closely the official installations manual. So far everything is up and running. But when uploading over LAN a collection of large files (>20GB) with the latest windows client Im experiencing connection drops.

Using Netdata for monitoring I can recognize a reproduceable pattern:

  1. The first 10GB are uploaded at almost 90MB/s.

  2. The HD writes constant with almost no read.

  3. Then after 10GB uploaded suddenly the HD begins to oscillate between read(40-80MB/s) and write(40-90MB/s).

  4. This then causes high cpu load as high as 60% due to iowait. At the same time the upload drops to zero.

  5. The server then stays in this read/write cycle for ~5-10min.

  6. At some time later, the windows client goes into a timeout and drops.

What I have tried:

-Tested it on a second rig

-Moved nextclouddata to a ssd

The measures above did not fix my problem. Although using the SSD the read/write cycle ends faster (5min). Because I can reproduce it on different hardware, I’m thinking about a configuration error in my lamp-stack.

My question(s):

  1. Is this read/write oscillation normal?

  2. Can I somehow prevent or delay it?

  3. Are there any obvious troubleshooting steps I should try?

Any tips/help is much appreciated. If needed I can provide logs(need to know which though).

Regards Digital