Consistent Hashing | Algorithms You Should Know #1

About this Video

• Video Title: Consistent Hashing | Algorithms You Should Know #1
• Channel: ByteByteGo
• Speakers: (Speaker name not explicitly mentioned in the transcript)
• Duration: 00:08:04

Introduction

This video explains consistent hashing, a technique used in large-scale distributed systems to distribute data evenly across multiple servers. It contrasts simple hashing, showing its shortcomings when servers are added or removed, and then details how consistent hashing, using a hash ring and virtual nodes, addresses these issues to minimize data movement.

Key Takeaways

• Simple Hashing Limitations: Simple hashing, using the modulo operation, redistributes almost all data when servers are added or removed, causing performance issues.
• Consistent Hashing Solution: Consistent hashing maps both objects and servers onto a hash ring. Object placement is determined by clockwise traversal from the object's position on the ring until a server is found. This minimizes data redistribution when the number of servers changes.
• Virtual Nodes for Even Distribution: Virtual nodes, representing multiple locations for each server on the hash ring, improve the even distribution of objects across servers, mitigating the unevenness that can occur with a simple hash ring.
• Real-world Applications: Consistent hashing is used in databases (DynamoDB, Cassandra), content delivery networks (Akamai), and load balancers (Google Load Balancer) for efficient data distribution and minimizing disruptions during server changes.
• Trade-offs: Using virtual nodes requires more metadata storage to manage the additional virtual node locations.