Scylla is an open-source distributed NoSQL database. It is compatible with Apache Cassandra, and uses the same protocols (Cassandra Query Language and Thrift) and same file formats (SSTable). It is optimized for workloads that requires low latency and high throughput, in addition to Apache Cassandra's high availability, scalability and fault-tolerance guarantee. Scylla uses a shared-nothing model and shard-per-core architecture, where each thread executes on its own CPU core, memory, and multi-queue network interface controller. Cross-core communication is carried out by explicit message passing, using an event-driven asynchronous programming model, Seastar.
Scylla supports non-blocking checkpoints through per-node backup procedures, which include full backup/snapshots and incremental backup. Snapshots are taken by the snapshot operation provided by the nodetool utility, while the incremental backup option can be configured in the configuration file. Automatic unnecessary backup cleaning is not implemented.
Multi-version Concurrency Control (MVCC)
Scylla does not support ACID transactions as in RDBMS. However, CQL has a BATCH
statement that allows multiple update statements belonging to a given partition key be applied in isolation (note that batches are not a full analogue for SQL transactions). Besides, in UPDATE
, INSERT
, and DELETE
statements, modifications belonging to the same partition key are performed atomically and in isolation. Scylla implements Multi-version Concurrency Control (MVCC) for partition mutation.
Scylla uses a shared-nothing model. Nodes in the cluster are organized in a decentralized consistent hashing ring and data is partitioned into shards by the key across all nodes. Scylla uses a shard-per-core architecture, where each thread for a shard executes on its own CPU core, memory, and multi-queue network interface controller. Cross-core communication is carried out by explicit message passing. Scylla also uses replicas for fault-tolerance.
https://github.com/scylladb/scylla
ScyllaDB Inc.
2014
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