Defining Failure Domains

Based on the levels of hierarchy described above, you can use the pstorage set-attr command to define failure domains for proper file replica allocation:

# pstorage -c <cluster_name> set-attr -R -p /failure-domain=<disk|host|rack|row|room>

where

• disk means that only 1 replica is allowed per disk or chunk server,
• host means that only 1 replica is allowed per host (default),
• rack means that only 1 replica is allowed per rack,
• row means that only 1 replica is allowed per row,
• room means that only 1 replica is allowed per room.

You should use the same configuration for all cluster files as it simplifies the analysis and is less error-prone.

As an example, do the following to configure a 5-rack setup:

1. Assign 0.0.1 to /etc/pstorage/location on all hosts from the first rack, 0.0.2 on all hosts from second rack, and so on.
2. Create 5 metadata servers: 1 on any host from the first rack, 1 on any host from second rack, and so on.
3. Configure Parallels Cloud Storage to have only 1 replica per rack (assuming that the cluster name is pcs1 ):

   # pstorage -c pcs1 set-attr -R -p /failure-domain=rack

4. Create CS services with the pstorage-make-cs command as described in Setting Up Chunk Servers .