6.3 HP StoreAll Storage File System User Guide (TA768-96093, June 2013)

13 Using remote replication
This chapter describes how to configure and manage the Continuous Remote Replication (CRR)
service.
NOTE: Keep in mind that when you set up CRR, the Express Query database is not replicated.
You must set up periodic exports as described in “Metadata and continuous remote replication”
(page 221).
Overview
The CRR service provides a method to replicate changes in a source file system on one cluster to
a target file system on either the same cluster (intra-cluster replication) or a second cluster (inter-cluster
replication). Both files and directories are replicated with remote replication, and no special
configuration of segments is needed. A remote replication task includes the initial synchronization
of the source and target file systems.
When selecting file systems for remote replication, you should be aware of the following:
• One, multiple, or all file systems in a single cluster can be replicated.
• Remote replication is a one-way process. Bidirectional replication of a single file system is not
supported.
• The mountpoint of the source file system can be different from the mountpoint on the target
file system.
• The directory path /mnt/ibrix is reserved for use by CRR for internal operations. Do not
use the /mnt/ibrix path for mounting any file systems, including ibrix. The CRR feature
does not work properly if /mnt/ibrix is occupied by another file system mount.
Remote replication has minimal impact on these cluster operations:
• Cluster expansion (adding a new server) is allowed as usual on both the source and target.
• File systems can be exported over NFS, SMB, FTP, or HTTP.
• Source or target file systems can be rebalanced while a remote replication job is in progress.
• File system policies (ibrix_fs_tune) can be set on both the source and target without any
restrictions.
The Fusion Manager initializes remote replication. However, each file serving node runs its own
replication and synchronization processes, independent of and in parallel with other file serving
nodes. The individual daemons running on the file serving nodes perform the actual file system
replication.
The source-side Fusion Manager monitors the replication and reports errors, failures, and so on.
Continuous or run-once replication modes
CRR can be used in two modes: continuous or run-once.
Continuous replication. This method tracks changes on the source file system and continuously
replicates these changes to the target file system. The changes are tracked for the entire file system
and are replicated in parallel by each file serving node. There is no strict order to replication at
either the file system or segment level. The continuous remote replication program tries to replicate
on a first-in, first-out basis.
When you configure continuous remote replication, you must specify a file system as the source.
(A source directory cannot be specified.) File systems specified as the replication source or target
must already exist. The replication starts at the root of the source file system (the mount point).
178 Using remote replication