Storage Services: OBS, EVS, and SFS
Storage models
- OBS is object storage accessed over HTTP/HTTPS APIs. Bucket names are globally unique, and storage classes include Standard, Infrequent Access, Archive, and Deep Archive. OBS supports lifecycle rules, versioning, WORM, and server-side encryption.
- EVS is block storage for a single ECS in the same AZ. Disk types include high-I/O SSD, general-purpose SSD, and HDD variants. Snapshots and encryption are available.
- SFS is shared file storage using NFS or CIFS, mounted by many ECS instances concurrently. SFS Turbo provides higher performance for latency-sensitive shared workloads.
Worked example
Twenty ECS instances need a shared read/write configuration directory, and a 5 TB log archive is accessed roughly once a year. Choose SFS for the shared directory because multiple instances must mount the same POSIX file system concurrently. Choose OBS Archive for the logs, with a lifecycle rule that transitions objects to Archive after 30 days. Reasoning: EVS cannot be attached to twenty instances at once, and SFS is inefficient for long-term cold data. OBS Archive minimizes storage cost, but retrieval takes longer and incurs retrieval fees.
Traps
Treating OBS as a normal block device for every workload; attaching one EVS disk to ECS instances in different AZs; using the wrong SFS protocol for Windows versus Linux clients; and ignoring Archive retrieval time and cost.