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Cloud · Extra High-Value

Object storage vs block storage

Easycloud-23
object storageblock storages3ebs

Question

What is the difference between object storage and block storage?

Solution

Object storage stores files as objects in buckets (S3, GCS, ADLS/Blob). You address them by key over HTTP APIs. Ideal for data lakes, backups, and shared analytics files.

Block storage is a disk volume attached to a VM (EBS, Persistent Disk, Azure Disk). The OS sees blocks/filesystems. Ideal for database data directories and boot disks.

Object:  app --HTTP--> s3://bucket/file.parquet   (many readers)
Block:   VM  --attach--> /dev/xvdf mounted at /data (one instance*)

\*Some cloud disks can multi-attach in special cases; default mental model is one VM.

Comparison

| | Object | Block | |---|---|---| | Interface | Object API / keys | Disk / filesystem | | Sharing | Easy across services | Tied to compute (usually) | | Use in DE | Lake files, Parquet, logs | DB volumes, local shuffle disks | | Metadata | Rich object metadata | FS metadata |

Interview tip: Lakes use object storage; databases usually sit on block volumes. Spark reads Parquet from object storage, but executors may still use local block disks for shuffle spill.

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