Veritas InfoScale™ 7.0 Replication Administrator's Guide - Linux

Storage Replicator Log (SRL)

The Storage Replicator Log (SRL) is a circular buffer of writes for an RVG. Each RVG contains one SRL. Writes to the data volumes in the RVG are first queued in the SRL on the Primary host before they are sent to the Secondary. VVR uses the SRL to track the order of writes to data volumes in the RVG. The SRL enables VVR to maintain write-order fidelity at the Secondary RVG.

In addition to the replication functionality, the SRL provides the functionality provided by the DRL (Dirty Region Log). Therefore, VxVM DRL logging is explicity disabled when a volume is added to an RVG.

From a VxVM perspective, the SRL is just another volume. Because all writes are written to the SRL first, it is important for the SRL to have optimum write performance. This means all performance techniques used to increase write performance of a volume apply to the SRL. For most implementations, the SRL is striped across multiple drives for write performance, and mirrored to an equal set of drives for protection.

Each write to the disks generates two writes: one to the SRL, and one to a data volume. For this reason, it is recommended that the data volumes and SRL volumes should be located on different physical disks or RAID sets to improve write performance. Note that VVR uses the SRL log internally. Application writes directly to the SRL are not allowed.