Amazon Elastic Block Store (EBS)
- What it is
- Block storage volumes attached over the network to a single EC2 instance — behaves like a raw hard drive.
- Persists independently of the instance lifecycle: terminate the instance, keep the volume.
- Key constraints
- Locked to one Availability Zone. The instance and the volume must be in the same AZ.
- Attaches to one instance at a time (except io1/io2 Multi-Attach within an AZ).
- Volume types
- gp3 / gp2 — general purpose SSD. Default choice. gp3 lets you set IOPS independently of size.
- io1 / io2 Block Express — provisioned IOPS SSD, for critical high-performance databases.
- st1 — throughput-optimized HDD, for big sequential workloads (log processing, data warehouses).
- sc1 — cold HDD, cheapest, for infrequently accessed data.
- Snapshots
- Incremental backups stored in Amazon S3 behind the scenes. Region-scoped, so a snapshot is how you move a volume to another AZ or Region.
- Not to be confused with
- Instance store — physically attached, faster, but ephemeral; data dies with the instance.
- Amazon Elastic File System (EFS) — shared across many instances and AZs; EBS is one instance, one AZ.