6.5 HP StoreAll OS User Guide

14 Using continuous remote replication
This chapter describes how to configure and manage the Continuous Remote Replication (CRR)
service.
NOTE: Be aware that when you configure CRR, the Express Query database is not replicated.
To replicate custom metadata from the Express Query database and you are running StoreAll OS
6.5 or later, see “Enabling and disabling custom metadata replication ” (page 260). If you are
running an earlier version of StoreAll OS, see “Metadata and continuous remote replication” (page
298) for more information.
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.
• CRR supports directory paths no longer than 4096 characters.
• Replication is not supported between a file system running version 6.5 and a target file system
running version 6.3 if Express Query is enabled on the source file system.
• If a file system is enabled as case_insensitive and will be used for replication, ensure that you
enable case_insensitive on both the source and target file systems.
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 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
248 Using continuous remote replication