Data Model

Hierarchical

Splunk is a NoSQL database management system. Its data model is a hierarchical search-time mapping of data. The knowledge managers on a Splunk instance design the data model.

Joins

Not Supported

Splunk supports inner (default), outer, and left joins using the join command. This works best when the results of the subsearch are less than 50,000 rows.

It can also join a search result set with itself using the selfjoin command.

Hardware Acceleration

GPU FPGA

FPGA and GPU can be used to accelerate Splunk's performance.

Concurrency Control

Not Supported

Splunk supports concurrent search but limits the number in order to preserve performance. It also allows you to configure the maximum number of concurrent searches between scheduled and summarization queries based on your usage.

Splunk also supports concurrent users. A user uses exactly one CPU core on each indexer for the duration of the search. By default, a search on Splunk cannot use multiple cores.

Checkpoints

Not Supported

Splunk supports the notion of checkpoints. When reading data and indexing, a checkpoint can be created to mark the data as being read or indexed.

Indexes

B+Tree

Splunk adds all incoming data to indexes after processing it. It indexes data by breaking them into events, based on the timestamp. After breaking the data up into events, the events are passed through the indexing pipeline where additional steps are taken, such as breaking the events into segments so indexing and searching can be done efficiently, building data structures for the indexes, and writing the events out to disk.

Splunk supports events and metrics indexes. Events indexes are the default index type, impose minimal structure, and can accommodate any type of data. Metrics indexes are highly structured and designed to handle high volume and low latency demands. These indexes have better performance and less space utilization compared to events indexes.

Logging

Not Supported

Scripts in Splunk can send logging data to splunkd.log for tracking and troubleshooting using the stderr command. It supports 5 log levels:

• DEBUG
• INFO
• WARN
• ERROR (default)
• FATAL

Compression

Naïve (Record-Level)

Splunk compresses the raw data up to approximately half its original size. For indexes, Splunk supports gzip (default), lz4, and zstd for compression and can handle different buckets compressed with different algorithms.

Storage Model

Custom

Splunk stores data in a flat file format. All data in Splunk is stored in an index and in Hot, Warm, and Cold buckets depending on the size and age of the data. It supports both clustered and non-clustered indexes.

Foreign Keys

Supported

Splunk supports referential integrity.

Storage Architecture

Disk-oriented

Splunk is disk-oriented.

Isolation Levels

Not Supported

In Splunk, workload management allows resource isolation search and ingest processes. This lets users allocate resources to search pools without affecting ingest processes.

Query Execution

Vectorized Model

Splunk uses MapReduce to speed up searches.

Views

Not Supported

Splunk's Web Framework includes a library of views (such as Chart, Table, SplunkMap, Timeline, etc.), UI widgets that allow you to display certain data in certain ways.