For higher read parallelism and larger volumes of storage per server, you may want to
configure servers to store data in multiple directories on different devices. Once a server is
started, you must go through the following steps to change the directory configuration.
You can add or remove data directories to an existing master or tablet server via the
kudu fs update_dirs tool. Data is striped across data directories, and
when a new data directory is added, new data will be striped across the union of the old and
new directories.
The tool can only run while the server is offline, so establish a maintenance window
to update the server. The tool itself runs quickly, so this offline window should be
brief, and as such, only the server to update needs to be offline.
However, if the server is offline for too long (see the
follower_unavailable_considered_failed_sec flag), the tablet replicas
on it may be evicted from their Raft groups. To avoid this, it may be desirable to bring
the entire cluster offline while performing the update.
Run the tool with the desired directory configuration flags. For example, if a cluster
was set up with --fs_wal_dir=/wals, ‑‑fs_metadata_dir=/meta, and ‑‑fs_data_dirs=/data/1,/data/2,/data/3, and /data/3 is to be
removed (e.g. due to a disk error), run the command:
$ sudo -u kudu kudu fs update_dirs --force --fs_wal_dir=/wals --fs_metadata_dir=/meta --fs_data_dirs=/data/1,/data/2
Modify the values of the fs_data_dirs flags for the updated sever.
If using Cloudera Manager, make sure to only update the configurations of the
updated server, rather than of the entire Kudu service.
Once complete, the server process can be started. When Kudu is installed using system
packages, service is typically used:
