Improve Performance and Data Availability with Elastic Block Store (EBS) Posted on : May 06 - 2022

Nowadays, many Database-as-a-Service (DBaaS) solutions separate the computation layer and the storage layer. These include, for example, Amazon Aurora and Google BigQuery. This solution is attractive, as the data storage and data replication can be handled by existing services. DBaaS takes off the need to worry about this complexity; however, the performance of this design sometimes may not be as good as the traditional ways – using a local disk as storage. 

In this blog, we show that with a careful selection of Elastic Block Store (EBS) types and clever optimizations, deploying DBaaS on EBS can achieve even better performance than on local disks.

Why do we consider EBS in the first place?

To explain our motivation for using EBS, we’d like to briefly introduce TiDB. TiDB is a MySQL-compatible, distributed database. TiDB Servers are the computation nodes, which process SQL requests. The Placement Driver (PD) is the brain for TiDB, which configures load balancing and provides metadata services. TiKV is a row-oriented key-value store that processes transactional queries. TiFlash is a columnar storage extension that handles analytical queries. In this blog, we focus on TiKV.

TiKV provides distributed key-value service. First, it splits the data into several Regions, the smallest data unit for replication and load balancing. To achieve High Availability (HA), each Region is replicated three times and then distributed among different TiKV nodes. The replicas for one Region form a Raft group. Losing one node, and thus losing one replica in some Regions is acceptable for TiDB. However, losing two replicas simultaneously causes problems, because the majority of members of a Raft group are lost. This makes a Region unavailable; its data can no longer be accessed. Human intervention is needed to address such issues. View More