bionandco.blogg.se - Cassandra database

The storage engine’s default commit log is set to sync periodically every 10 seconds.

Similar to the consistency problem, durability guarantee is also a tradeoff between performance and correctness.

In the object storage world, the implication is that you can be good for archival use cases (write once, read very infrequently) or you choose a different architecture. It is important to apply this consistency setting for both read and write operations in addition to the object data operations performed outside of it. Any setting other than QUORUM or ALL means you are at risk of reading stale data. When employing Cassandra as a metadata database for an object store, you can either be fast or consistent - but not both at the same time.Ĭassandra’s tunable consistency is a compromise, not a feature. Meaning it trades Consistency for Availability and Partition tolerance.

Cassandra is categorized as an AP system in CAP.

While Cassandra supports atomicity and isolation at the row-level, it trades transactional isolation and atomicity for high availability and fast write performance. Further, there is no capacity to roll back transactions in the event of a failure. Cassandra does not support joins or foreign keys, and consequently does not offer consistency in the ACID sense.

It does not have the rigidity to prevent partially successful writes, dupes, contradictions and the like. Cassandra was never designed to manage file or object storage metadata and it is predictably weak in this regard.Let’s explore why in a little more detail. Object storage needs are far simpler and different from what Cassandra is built for.īecause the implications of employing Cassandra as a object storage metadata database were not properly understood, many object storage vendors made it a foundational part of their architecture - unfortunately it keeps them from ever moving past simple archival workloads into the modern workloads that define the future of object storage (AI/ML, analytics, web/mobile applications). However, using Cassandra as a metadata database for an object storage system introduces significant complexity resulting in data integrity and performance issues at scale - particularly if one wants to use their object store as a primary storage system.

Cassandra's eventual consistency model and lack of transactions, multi-table support like joins, subqueries can also limit its usefulness. Like any powerful tool, Cassandra has its ideal use cases - in particular, Cassandra excels at supporting write-heavy workloads, while having limitations when supporting read-heavy workloads. Cassandra is a popular, tried-and-true NoSQL database that supports key-value wide-column tables.