[Question posted by a user on YugabyteDB Community Slack]
I did some reading in the docs and found fs_data_dirs. Does yugabyte-db automatically split the tablets evenly in the data dirs?
The flag fs_data_dirs sets the directory or directories for the tablet server or master where it will store data on the filesystem. This should be specified as a comma-separated list.
This data is logging, metadata, and data. The first directory will get the logging, all the directories will get the WAL and rocksdb databases. The tablets which is the storage foundation of a table or index are distributed over the directories in a round-robin fashion. This indeed happens completely automatically.
It might be confusing to talk about splitting because when a YSQL table or secondary index is created, the create statement allows you to explicitly define how many tablets the object is split, which is what is distributed over the directories specified. At the risk of making it confusing, there is another feature which is called automatic tablet splitting, which is a feature set by the flag ‘--enable_automatic_tablet_splitting’ set in the masters, which is the mechanism of making YugabyteDB automatically split tablets when it deems tablets getting too big, and thus allows you to start with a single tablet, which will then be split automatically.