Explore scylladb data_file_directories

[VAveryanov8]

Accordingly to scylladb configuration (link ), data_file_directories is a list, but it's not clear what the behavior of scylladb and how it handles it if multiple values were provided.
From the scylla-manager perspective only first entry is considered when backup/restore operations are executed.

Explore what is the scylladb behavior and based on the result we can decide what to do next.

[VAveryanov8]

According to information that was kindly provided by @xemul, currently scylladb only uses first entry from data_file_directories for write/read, but it's likely a bug, because expected behavior is to load sstables from all entries during the boot process and to write (put) data only to the first entry.