In this post we discuss what HBase users should know about one of the internal parts of HBase: the Memstore. Understanding underlying processes related to Memstore will help to configure HBase cluster towards better performance.

HBase Memstore

Let’s take a look at the write and read paths in HBase to understand what Memstore is, where how and why it is used.

Memstore Usage in HBase Read/Write Paths Memstore Usage in HBase Read/Write Paths

(picture was taken from Intro to HBase Internals and Schema Design presentation)

When RegionServer (RS) receives write request, it directs the request to specific Region. Each Region stores set of rows. Rows data can be separated in multiple column families (CFs). Data of particular CF is stored in HStore which consists of Memstore and a set of HFiles. Memstore is kept in RS main memory, while HFiles are written to HDFS. When write request is processed, data is first written into the…

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