This topic describes the file storage of PolarDB O Edition.

  • The data and WAL logs of the primary node and read-only nodes are stored in shared storage.
  • The configuration files, log files, and temporary files are stored on each node.
  • The commit log (clog) file of the primary node is stored in shared storage. The clog file of a read-only node is maintained on the read-only node.
  • The pg_control file of the primary node is stored in shared storage. The pg_control file of a read-only node is read from the shared storage only when the database is started, and maintained in the memory after the database is started.
File storage
Directory or file Description Storage path
base The subdirectory of each database. Shared storage
global The directory of cluster-wide tables.
pg_tblspc The table space.
pg_wal The directory of write-ahead logging (WAL) logs.
pg_dynshmem The file that is used by the dynamic shared memory. One copy on each node
pg_snapshots The exported snapshots.
pg_replslot The replication slot data.
pg_stat_tmp The temporary files for the statistics subsystem.
pg_stat The persistent files for the statistics subsystem.
pg_serial The information about committed serializable transactions.
pg_xact The transaction log file.
  • Shared storage for the primary node
  • One copy on the on-premises storage for read-only nodes
pg_commit_ts The time when the transaction is committed.
pg_multixact The information about sub-transactions.
pg_version The version information. One copy on each node
postgresql.auto.conf The parameter configuration file, which has a higher priority over the postgresql.conf file.
postmaster.opts The file that records the database parameters that are specified before a server start.
postmaster.pid A lock file that records information such as the process ID of postmaster, database directory, start time of postmaster, and port number.
postgresql.conf The configuration file of parameters.
pg_hba.conf The file that is used to control client authentication.
pg_ident.conf The file that records mappings between the names of operating system users and database users.