What is Cisco ACI shards?

In Cisco ACI, a "shard" is an essential unit of the ACI database, or a group of database rows distributed across the APIC nodes in the APIC cluster. It is used to enable parallel processing and data protection in the event of an APIC failure. Each APIC database shard has exactly three replicas that are distributed across the APIC cluster based on shard layouts defined for each cluster size.

Simplify Cisco ACI Clustering and Sharding (Must-Know Tips)

At the heart of the Cisco ACI lies a critical component known as the Application Policy Infrastructure Controller (APIC). This powerhouse controls the policy management and the network configuration, forming the brain of the ACI. But what makes it truly fascinating is the concept of “ACI Clustering & Database Sharding“.

In this video, I’m going to explain how the Cisco APIC Cluster works and what database sharding is all about. We’ll see how it drives scalability, redundancy, and resilience within the ACI fabric management plane.

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Summary

Cisco ACI fabric scalability depends on the APIC appliance type (M/L) and the APIC cluster size (3-APICs/5-APICs .. etc).
The ACI database is replicated and broken up into smaller database units called shards.
The larger the APIC cluster we have, the more scalability we gain, NOT high availability
A failure of two APICs will cause some shards to be in the minority state, and losing three APICs will cause some/all shards to be lost.
For more information about the scalability of Cisco APIC, check the Verified Scalability Guide for Cisco APIC.

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Salman Alhiary Expert Network Consultant

In the networking field since 2010, 2× CCIE (ENT & DC), and founder of LearnWithSalman—specializes in Cisco Data Center networking and automation. A former Cisco TAC engineer and now an Expert Professional Services consultant, he delivers lab-first tutorials, deep templates, and repeatable playbooks through his courses and technical blog, all built from real enterprise projects.

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