DVA C02 Notes - Storage

EBS (Elastic Block Store)

• AZ-scoped storage (tied to one AZ)

• Can move across AZ/region using snapshots

• Block storage (like a disk)

• Attached to EC2 → needs filesystem (ext4/xfs)

Multi-Attach

• Only io1/io2

• Same AZ only

• Max 16 instances

• Supports concurrent read/write

• ❗ Requires cluster-aware filesystem (AWS doesn’t handle locking)

EFS (Elastic File System)

• Regional service (multi-AZ by default)

• File storage (NFS)

• Can be mounted to 100s of EC2 instances at the same time

• Linux only

• Auto-scaling (capacity planning available via provisioned option)

• Higher cost than EBS

• Lifecycle policies used to move data to cheaper tier based on Last accessed.

Instance Store (Ephemeral Storage)

• Physically attached storage to EC2 instance

• Provides very low latency and high IOPS

• Ephemeral (temporary storage)

Data behavior:

• Lost on instance STOP or TERMINATION

• NOT lost on reboot

Key characteristics:

• No persistence

• No snapshots or backup

• Not detachable or reusable

Use cases:

• Caching (Redis, Memcached)

• Temporary / scratch data

• Buffer storage

• HPC intermediate processing

Key decision rule:

• Use Instance Store when data can be LOST

• Use EBS when data MUST persist

One Liner

• Single instance → EBS

• Multi-instance, same AZ → Multi-Attach EBS

• Multi-instance, cross-AZ → EFS

• Shared file system without management → EFS

• EBS => One server mindset

• EFS = Shared storage mindset

• Instance storage Highest I/O performance among EC2-attached storage

  • No network overhead (physically attached)

  • Very low latency