Block Storage (EBS / Persistent Disk)

Definition

A storage architecture that splits data into evenly sized blocks and stores them independently. It acts exactly like a raw physical hard drive (SSD/HDD) attached directly to a specific virtual machine.

Explain Like I'm New

The C: Drive or D: Drive of your cloud server. It is incredibly fast, allows you to install operating systems, and acts exactly like a normal hard drive.

Real World Example

AWS EBS, Azure Managed Disks, GCP Persistent Disk. When you launch a new Virtual Machine, you attach a 50GB Block Storage volume to it so the VM has a place to install Linux and the database files.

Common Use Cases

•Operating System boot drives
•High-performance databases

Interview Questions

basic

If you terminate/delete a Virtual Machine, what happens to its attached Block Storage drive?

intermediate

Why would you choose Block Storage for a massive database instead of Object Storage (S3)?

Flash Cards

Question

What happens on termination?

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Answer

By default, the primary boot drive is deleted when the VM is terminated. However, you can configure the settings to save the drive, allowing you to attach it to a new VM later.

Question

Block vs Object for DB?

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Answer

Because of speed and updates. If you change 1 single letter in a 5GB file on S3, you have to re-upload the entire 5GB file. Block storage allows you to update just the exact microscopic block of data on the disk, which is required for database performance.