/opt/trains/data contains data stored by ElasticSearch and MongoDB, which you can't delete manually (this will break each service and Trains Server as well).
You can clean up files uploaded to Trains File Server which are located in /opt/trains/data/fileserver - deleting those will simply mean the WebUI will not be able to find them when trying to display experiment data, so if you have very old files related to old experiments that you don't need any more, you can remove them from that folder.
Experiments cleanup can be done using the APIClient tool (see here: https://github.com/allegroai/trains-server/issues/53#issuecomment-660667572 ) - this will clean up both MongoDB and ElasticSearch data.
SuccessfulKoala55 Ok! What best praktik to clear old data from Trains? If I remove data from /opt/trains/data, Trains not brake&
Hi ItchyHippopotamus18 , what exactly are you trying to configure? If you're referring to the disk usage by Trains Server, all the data is stored under the various folder inside /opt/trains/data , so mounting this to a different location or changing this value in the configuration will cause the system to place the database data in a different location