Both. Native persistence in Ignite can be turned on and off. This allows Ignite to store data sets bigger than can fit in the available memory. Essentially, smaller operational data sets can be stored in-memory only, and larger data sets that do not fit in memory can be stored on disk, using memory as a caching layer for better performance.
Yes. Even though Ignite durable memory works well in-memory and on-disk, the disk persistence can be disabled and Ignite can act as a distributed in-memory database, with support for SQL and distributed joins.
Yes. Ignite is a full-featured data grid, which can be used either in memory-only mode or with Ignite native persistence. It can also automatically integrate with any 3rd party databases, including any RDBMS or NoSQL store.
Yes. When native persistence is disabled, Ignite becomes a distributed cache. Ignite implements JCache specification (JSR 107) and provides a lot more functionality than required by the specification, including partitioned and replicated distribution modes, distributed ACID transactions, SQL queries, native persistence, and more.
Yes. Data in Ignite is either partitioned or replicated across a cluster of multiple nodes. This provides scalability and adds resilience to the system. Ignite automatically controls how data is partitioned, however, users can plug in their own distribution (affinity) functions and collocate various pieces of data together for efficiency.
Not fully. Although Ignite aims to behave like any other relational SQL database, there are differences in how Ignite handles constraints and indexes. Ignite supports primary and secondary indexes, however, the uniqueness can only be enforced for the primary indexes. Ignite also does not support foreign key constraints.
Essentially, Ignite purposely does not support any constraints that would entail a cluster broadcast message for each update and significantly hurt performance and scalability of the system.
Not exactly. Just like other NoSQL databases, Ignite is highly available and horizontally scalable. However, unlike other NoSQL databases, Ignite supports SQL and ACID transactions.
Not fully. ACID Transactions are supported, but only at key-value API level. Ignite also supports cross-partition transactions, which means that transactions can span keys residing in different partitions on different servers.
At SQL level Ignite supports atomic, but not yet transactional consistency. Ignite community plans to implement SQL transactions in version 2.4.
Yes. Ignite supports both, key-value and SQL for modelling and accessing data. In addition, Ignite provides strong processing APIs for computing on distributed data.
Yes. Ignite provides a feature rich key-value API, that is JCache (JSR-107) compliant and supports Java, C++, and .NET.
Ignite durable memory architecture allows Ignite to extend in-memory computing to disk. It is based on a paged-based off-heap memory allocator which becomes durable by persisting to the write-ahead-log (WAL) and, then, to main Ignite persistent storage. When persistence is disabled, durable memory acts like a pure in-memory storage.
Ignite is a distributed system and, therefore, it is important to be able to collocate data with data and compute with data to avoid distributed data noise. Data collocation becomes especially important when performing distributed SQL joins. Ignite also supports sending user logic (functions, lambdas, etc.) directly to the nodes where the data resides and computing on the data locally.
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