Azure Storage: types, tiers, redundancy
Storage account and services
A storage account is the namespace and billing container. Inside it, per the course analogies:
- Blob Storage (the filing cabinet): unstructured data. Images, video, backups, big data.
- Azure Files (the shared network drive): SMB file shares for Windows, macOS, Linux.
- Queue Storage (the office mailbox): messages for decoupled, async apps.
- Table Storage (the contact database): NoSQL key-value (Cosmos DB is the modern pick).
- Disk Storage (the VM hard drive): managed disks for VMs.
Account types: General-purpose v2 does everything and is the default answer. FileStorage is premium Azure Files; BlockBlobStorage is premium high-transaction blobs.
Data Lake Storage Gen2 is Blob Storage with the hierarchical namespace switched on, for big data analytics (Synapse, Databricks). Not a separate service. Performance tiers are Standard (HDD) and Premium (SSD).
Blob access tiers
- Hot: frequent access (the default). Highest storage cost, lowest access cost, no minimum stay.
- Cool: roughly monthly access. Cheaper storage, pricier access, 30-day minimum.
- Archive: compliance and long retention. Cheapest storage, must rehydrate, 180-day minimum.
Archive rehydration takes up to 15 hours standard, under 1 hour high priority (blobs under 10GB, costs more). No reading or editing while archived.
Lifecycle policies auto-move blobs between tiers and can delete old data (“Cool after 30 days, Archive after 180”).
The keyword mapping: frequent = Hot, monthly = Cool, seven-year retention = Archive.
Redundancy options
- LRS: 3 copies in one datacenter. Survives a rack or server failure. 11 nines durability.
- ZRS: 3 copies across zones. Survives a zone outage. 12 nines.
- GRS: 3 + 3 in the paired region. Survives a regional disaster. 16 nines.
- RA-GRS: GRS plus read access to the secondary, so you keep reading during an outage. 16 nines.
- GZRS: ZRS plus 3 in the paired region. Survives zones and regions. 16 nines.
- RA-GZRS: GZRS plus read on the secondary. The maximum. 16 nines.
The GRS secondary is invisible until Microsoft fails over; the RA- variants let you read it anytime.
The keywords: lowest cost = LRS, zone failure = ZRS, regional disaster = GRS+, read during outage = RA-.