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Azure Blob Storage

Azure Blob Storage is Microsoft Azure's managed object-storage service — the Azure peer of Amazon S3 and Cloudflare R2. It provides durable, replicated blob storage as a managed service.

In the wiki it is load-bearing as the authoritative durable layer in GitHub's rebuilt Git serving architecture. GitHub (owned by Microsoft, with a large Azure footprint) is moving the source of truth for repository data out of local fileserver disks (Spokes) and into Azure Blob Storage, which "already provides durability and replication at Azure scale." The compute layer above it becomes a pool of lightweight, stateless cache workers optimized for throughput at lowest latency. (Source: sources/2026-10-06-github-building-git-infrastructure-for-agent-scale-development)

Role in compute–storage separation

Placing authoritative data in a managed object store is the enabling move for compute–storage separation (the same shape as tiering storage to an object store):

  • Durability is the object store's job. GitHub no longer adds a durable replica to add read capacity.
  • Failure recovery becomes a cache miss. When a compute worker is lost, a replacement can serve immediately and fill its cache from Azure Blob Storage as traffic arrives — no full-repo rebuild.
  • Maintenance runs against durable storage. Separate compaction / GC workers operate directly on the object store, off the serving path.

As a quorum member: the "virtual replica" (2026-10)

The 2026-10-21 GitHub post makes the enabling move concrete: Azure Blob Storage joins the Spokes quorum as a special member — a "virtual replica." The compute that fronts it is GitHub's first fully ephemeral node, and it has two roles:

  • Virtual write replica — streams incoming writes to the blob store and serves no reads. Because it is a quorum member, a write is not acknowledged until it is durable in Azure Blob Storage — object-store durability becomes part of the commit path. It also coalesces transactions on disjoint references into a single set of network I/Os, so a busy repo pays for one object-storage round trip across many concurrent writes instead of one per write.
  • Virtual read replicas — warm their cache from Azure Blob Storage and serve reads without joining the quorum, treating the blob store as the source of truth and reconciling local state against it in the background.

This is the point where "durability is the object store's job" stops being a principle and becomes a wire protocol: the blob store is literally in the write quorum. (Source: sources/2026-10-21-github-the-bridge-to-agent-scale-git-infrastructure)

Stub page

Covered here only at the depth the GitHub agent-scale source requires: Azure Blob Storage as the durable authoritative layer under a compute–storage-separated Git serving tier. General Azure Blob Storage internals (tiers, redundancy modes, lifecycle) are not yet ingested.

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