Detection of media failures

The database server checks the return code when it first opens a chunk and after any read or write. Whenever the database server detects that a primary (or mirror) chunk device has failed, it sets the chunk-status flag to down (D). For information about chunk-status flags, see Mirror status flags.

If the database server detects that a primary (or mirror) chunk device has failed, reads and writes continue for the one chunk that remains online. This statement is true even if the administrator intentionally brings down one of the chunks.

After the administrator recovers the down chunk and returns it to online status, reads are again split between the primary and mirror chunks, and writes are made to both chunks.