> For the complete documentation index, see [llms.txt](https://mariadb.com/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://mariadb.com/docs/gridgain/gridgain-8/architecture.md).

# Architecture

How GridGain 8 works under the hood — its multi-tiered memory and storage, clustering and discovery, data distribution, and consistency model.

GridGain 8 is a distributed, memory-centric platform built on Apache Ignite. This section explains the concepts and internals behind it: how data is stored across memory and disk, how nodes form a cluster and discover each other, how data is partitioned and rebalanced, and how GridGain keeps data consistent. Understand these before configuring and operating a cluster.

## The Big Picture

GridGain 8 and GridGain 9 share the same architecture at the level of ideas. What differs between the two versions is how each idea is implemented.

* **Distributed cluster.** GridGain runs as a cluster of server nodes that together store and process data. Applications work with the cluster through clients and drivers.
* **In memory and on disk.** Data can be kept entirely in memory or persisted to disk, combining in-memory speed with disk durability.
* **B+ tree storage.** GridGain stores data in memory pages and organizes its indexes as B+ trees.
* **Hash partitioning.** Each table or cache is split into partitions. A hash of a record's key determines its partition, and the partitions are spread across the nodes of the cluster.
* **Distributed copies.** Each partition can be stored on several nodes, so data stays available when a node fails.
* **Data colocation.** Related records that share a colocation key are stored on the same node, so queries and computations over them run locally.
* **SQL, key-value, and compute.** You can work with the same data through SQL or a key-value API, and send computations to the nodes that hold the data.

## How GridGain 8 Implements It

| Concept                          | GridGain 8                                                                                                                                                                  | Read more                                                                                                                                                                                                                        |
| -------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| Cluster membership and lifecycle | Nodes find each other through node discovery. A cluster must be activated before it runs workloads, and the baseline topology defines the nodes that store persistent data. | [Clustering](/docs/gridgain/gridgain-8/architecture/cluster/clustering.md), [Baseline Topology](/docs/gridgain/gridgain-8/architecture/cluster/baseline-topology.md)                                                             |
| Memory and persistence           | A multi-tiered, page-based memory architecture organized into data regions, with Native Persistence (checkpointing and write-ahead log) for durability.                     | [Memory Architecture](/docs/gridgain/gridgain-8/architecture/storage/memory-architecture.md), [Native Persistence](/docs/gridgain/gridgain-8/architecture/storage/native-persistence.md)                                         |
| Partitioning                     | The affinity function maps keys to partitions using rendezvous hashing. Caches run in partitioned or replicated mode.                                                       | [Data Partitioning](/docs/gridgain/gridgain-8/architecture/data-distribution/data-partitioning.md)                                                                                                                               |
| Copies and consistency           | Backup partitions hold copies of each partition. Partition map exchange (PME) and rebalancing redistribute partitions when the topology changes.                            | [Backup Partitions](/docs/gridgain/gridgain-8/architecture/data-distribution/data-partitioning.md#backup-partitions), [Data Rebalancing](/docs/gridgain/gridgain-8/architecture/replication-and-consistency/data-rebalancing.md) |
| Colocation                       | The affinity key.                                                                                                                                                           | [Affinity Colocation](/docs/gridgain/gridgain-8/architecture/data-distribution/affinity-colocation.md)                                                                                                                           |
| SQL engine                       | H2 parses and optimizes queries and generates execution plans.                                                                                                              | [Introduction to SQL](/docs/gridgain/gridgain-8/gridgain8-development/accessing-data/sql/sql-introduction.md)                                                                                                                    |

## Architecture Topics

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[Cluster](/docs/gridgain/gridgain-8/architecture/cluster.md)
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How GridGain 8 nodes discover each other and form a cluster, how activation and baseline topology control the cluster lifecycle, and how the cluster protects itself from split-brain.
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[Data Distribution](/docs/gridgain/gridgain-8/architecture/data-distribution.md)
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How data is distributed and represented in a GridGain cluster, covering data partitioning, affinity colocation, and the key-value and SQL access models.
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[Replication and Consistency](/docs/gridgain/gridgain-8/architecture/replication-and-consistency.md)
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How GridGain keeps partition copies balanced and available as the cluster topology changes — full and historical rebalancing, and partition loss handling.
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[Multiversion Concurrency Control](/docs/gridgain/gridgain-8/architecture/mvcc.md)
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Multiversion concurrency control (MVCC) in GridGain 8, enabled through the TRANSACTIONAL\_SNAPSHOT atomicity mode, its limitations, and how to use it.
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[Storage](/docs/gridgain/gridgain-8/architecture/storage.md)
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GridGain's storage architecture — the multi-tiered memory architecture, native persistence for durable on-disk storage, and swapping as an extension of memory.
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