Here is the result of iotop (that i just discover thanks to you)
Seems to have an issue with jbd2/md1-8 !
For the nextcloud database, it’s 1016.87 MB
you should give large enough caches to the database.
I’m not sure, are you talking about this parameter innodb_buffer_pool_size ?
At the moment, it is set to 256M
Here are all this related parameters
# Read the manual for more InnoDB related options. There are many!
default_storage_engine = InnoDB
# you can't just change log file size, requires special procedure
#innodb_log_file_size = 50M
innodb_buffer_pool_size = 256M
innodb_log_buffer_size = 8M
innodb_file_per_table = 1
innodb_open_files = 400
innodb_io_capacity = 400
innodb_flush_method = O_DIRECT
Also thanks for sharing this topic, i will check this as soon as possible 