Blob storage & lifecycle

Access tiers, lifecycle policies, cost.

Blob storage is the workhorse of Azure Storage — durable object storage for files, backups, data lakes, and static content. Its access tiers and lifecycle management are the levers for balancing performance and cost.

Access tiers

Blob storage offers access tiers priced for different access patterns. Hot is for frequently-accessed data (highest storage cost, lowest access cost). Cool is for infrequently-accessed data kept at least 30 days (cheaper storage, higher access cost, still instant retrieval). Cold is cheaper still for rarely-accessed data. Archive is the cheapest for long-term retention but data is offline — retrieval takes hours (rehydration). The rule: match the tier to how often data is read, and remember that access and retrieval costs rise as storage cost falls, so a frequently-read blob in Archive can cost more than one in Hot. Set a default tier on the account and override per blob as needed.

#  TIER      STORAGE COST   ACCESS   RETRIEVAL
#  Hot       highest        cheapest  instant
#  Cool      lower          higher    instant  (>= 30 days)
#  Cold      lower still     higher    instant  (>= 90 days)
#  Archive   cheapest       highest   HOURS (offline, must rehydrate)
#
# Lifecycle rule: auto-tier and expire by age — no manual work.
#   day 0   → Hot
#   day 30  → Cool
#   day 90  → Archive
#   day 365 → delete

Lifecycle management and features

Manually moving blobs between tiers does not scale, so lifecycle management policies automate it: rules transition blobs to cooler tiers or delete them based on age or last access, cutting cost on data you rarely touch without any manual effort. Other useful features include soft delete (recover accidentally-deleted blobs within a retention window), versioning (keep prior versions), and immutability policies (WORM — write-once-read-many — for compliance). Blob storage also underpins many Azure scenarios: static website hosting, backup targets, and data lakes (with hierarchical namespace enabled for Azure Data Lake Storage Gen2). For an administrator, the combination of the right tier plus lifecycle automation is the primary way to keep storage costs under control as data grows.