documentdb-storage

name	documentdb-storage
description	Storage configuration guidance for Azure DocumentDB — when and how to use Premium SSD v2 high-performance storage, IOPS/bandwidth caps that are gated by compute tier (not disk size), Premium SSD v2 limitations (no CMK, migration paths, disk-hydration sequencing), and storage capacity change limits. Use when picking a storage type at cluster creation, sizing for I/O-intensive workloads, migrating from Premium SSD to Premium SSD v2, or sequencing compute/storage/HA changes on a Premium SSD v2 cluster.
license	MIT

Storage — Azure DocumentDB

Azure DocumentDB clusters use remote premium SSD storage. Two disk types are offered:

Storage type	IOPS / bandwidth scaling	Max IOPS	CMK	Use it for
Premium SSD (v1)	Scales with disk capacity — bigger disk → higher IOPS	20,000	✔️	Legacy clusters, scenarios that require CMK
Premium SSD v2	Decoupled from disk size — IOPS/bandwidth gated by compute tier	80,000	❌	New production clusters; any I/O-intensive workload

Premium SSD v2 is the default recommendation for new clusters. It delivers up to a 12× performance boost at no added cost by removing the disk-size lever from the IOPS equation — you size storage for capacity and size compute for throughput, independently.

How Premium SSD v2 changes sizing

On Premium SSD v1, hitting 20,000 IOPS required provisioning a 20 TB disk even when only ~1 TB of data was stored. On Premium SSD v2, the highest achievable IOPS and bandwidth for the chosen compute tier are auto-configured regardless of disk size:

• Choose storage size based on how much data the cluster will hold.
• Choose compute tier based on how much IOPS / MBps the workload needs (see storage-tier-iops-caps).
• No knobs to tune — the upper-bound IOPS/bandwidth for the tier are applied automatically at no extra cost.

Rules

• storage-choose-premium-ssdv2 — When to pick Premium SSD v2 vs Premium SSD; the CMK trade-off.
• storage-tier-iops-caps — Compute-tier → max IOPS / MBps table; size compute for throughput, not disk for IOPS.
• storage-premium-ssdv2-limitations — Known limits: no CMK, capacity-change cap, replication restrictions, no online v1→v2 migration.
• storage-disk-hydration-sequencing — Space out compute scale / storage scale / HA-enable operations while the disk is hydrating.

References

• Premium SSD v2 disks — Azure DocumentDB