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Additional advantages of the Consistency Checking feature in Pivotal GemFire

Environment 

Product Version
Pivotal GemFire 7.0.x or later
OS All supported OS

Introduction

According to the User's Guide, the Consistency Checking feature is useful for replicated regions in order to maintain data consistency for concurrent updates (the section "Replicated Region Consistency" at User's Guid). On the other hand, it is not required for partitioned regions, because GemFire maintains data consistency for these regions by routing all updates on a given key to the GemFire member that holds the primary copy of that key (the section "Partitioned Region Consistency" at User's Guide). However, the Consistency Checking feature is available for partitioned and other non-replicated regions.

The question, then, is, "what is the advantage of Consistency Checking for these other types of regions?"

Description

In the case of persistent regions, the main advantage of Consistency Checking is to minimize recovery time.

When a member goes offline and comes back later, it will get some data from existing members. If this is the entire data set, recovery can take some time. However, in the case of persistent regions, it does not have to get the entire data set from the existing members. The restarted member can recover its local data from local disk store for persistent regions first, and then request a delta of changes that occurred while it was offline. It can do this because, with Consistency Checking, GemFire tracks entry versioning information and can recognize a delta of changes.

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