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This document identifies the 3 types of file replication that the optional Sun StorEdge[TM] File Replicator (SFR) software license provides when purchased for use on the Sun StorEdge[TM] 5210 NAS Appliance (SE5210), Sun StorEdge[TM] 5310 NAS Appliance (SE5310) and Sun StorEdge[TM] 5310C NAS Gateway Appliance (SE5310C).

Sun StorEdge File Replicator Software

SFR is supported on both the SE5210 and SE5310. Replication is supported between NAS systems from different families (ie. SE5210 to SE5310) as long as they are on the same build of OS.

NOTE: For the purposes of this document, the terms NAS OS "File System" and "volume" are synonymous.

Details

1. Replication is done on a volume by volume basis.

2. Replication is done from a volume on one system to unused space on the other.

3. Replication takes place at the block level.

4. A private network or VLAN is recommended for replication.

5. File Replicator requires a dedicated port on the Sun StorEdge[TM] 5000 Family NAS head.

Source and Target systems can be SE5310-FC, SE5310-SATA or SE5310C (with FC or SATA1) provided they all have the same version of software and are all licensed for SFR.

6. Replication support is "near synchronous".

7. Replication occurs for each record written to the source file system by staging into cache for replication to the target file system.

8. Replication can be one-to-one, many-to-one, or two-way (cross-mirror)

one-to-one

One volume may be replicated from a source to a single target volume.

Multiple volumes from a single source system can be replicated to multiple volumes on a single target system.

many-to-one

Multiple volumes from multiple source systems can be replicated to multiple volumes on a single target system.

two-way (cross-mirror)

Target systems may also be source systems but with different volumes.

Considerations

• Target volumes cannot be accessed during normal state operations of replication.
• Target volumes cannot be backed up without breaking the mirror and promoting
  the target volume.
• Target volumes cannot be accessed for read or write by any other user or applications without breaking the mirror and promoting the volume.

Cluster Considerations

SE5310C with SFR

All 3 types of replication are supported with the SE5310C but only on a single system (head) of a cluster as a source or as a target.

Replication is supported on SE5310C with the following restriction:

Only one system of the Cluster may be either the Source or the Target of the replication. The implications of this limitation are that either some of the data cannot be replicated or that all active data must be dedicated to one system of the cluster resulting in an active-passive system with some level of unused storage.

To illustrate:

• Source system is a cluster with System A and System B
• Target system is a cluster with System A' and System B'

If data is balanced between System A and System B on the source system, only data from System A can be replicated to the target System A' and leaves the data on Source System B unreplicated.

If all the data from the clustered system must be replicated then all the data must be allocated to the Source System A which can then be replicated to Target System A'. Source System B has no data and therefore remains passive and, since Source System B must have at least one volume allocated to it, that volume becomes wasted space (since no data is allocated to system B).

Both systems of a cluster must be licensed for replication.

Both systems of a cluster must offer NAS services to the network and own volumes and file systems (file systems on one of the systems of the cluster can not be replicated).

Clusters may be a source system, a target system or both (provided that the source file system(s) and/or target file system(s) reside only on one system within the cluster.

SE5310C failover with replication

Source Cluster Systems can fail over from either system without impacting replication.

When a source or target SE5310C system is in "fail over" state, new replication sources cannot be created but the existing replications will continue to operate.

This implies that, if mirrors are broken during the "fail over" state, the cluster must "fail back" before the mirror can be re-established.

Target SE5310C systems can fail over from either system without impacting replication.

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