# Commvault Flex Appliance Capacity Planning Guidelines

## Size Flex Nodes Based on BET

The primary sizing metric for Flex is Back-End Terabytes (BET) after deduplication and compression. The Commvault Solution Design Tool should always be used for determining the number of nodes, however the rule of thumb is 1 node per every 500TB of BET.

Protected Capacity (BET) | Recommended Flex Nodes
--- | ---
Up to 500 TB | 2 nodes (minimum deployment)
500 TB – 1 PB | 2–3 nodes
1 PB – 1.5 PB | 3 nodes
1.5 PB – 2 PB | 4 nodes
2 PB – 3 PB | 6 nodes
3 PB – 5 PB | 6–10 nodes
5 PB+ | Use CSDT for detailed sizing

Example: A customer with 1.8PB BET would typically start with 4 Flex nodes, distributing approximately 450TB per node.

## Avoid Running Nodes at Maximum Capacity

Although each node supports up to 500TB BET, it is generally better to design with operational headroom. Recommended utilization:

Design Target | BET per Node
--- | ---
Conservative | 300–350 TB
Typical Enterprise | 350–450 TB
Maximum Supported | 500 TB

This provides room for: - Data growth - Increased backup concurrency - Faster recovery operations - Cyber recovery workloads

## Size for Recovery Performance

Node count should not be based solely on storage capacity.

Consider adding nodes when customers require:

- Aggressive RTOs
- Large-scale restore operations
- AI and analytics workloads
- High daily ingest rates
- Large database environments

More Flex nodes provide:

- Greater aggregate throughput
- More parallel backup streams
- Faster restore performance
- Better workload distribution

This is one of the reasons the architecture shifted from 1PB/node to 500TB/node.

## Scale Compute and Storage Independently

One of Flex's key advantages is that compute and storage scale separately.

Add Flex nodes when:

- Performance requirements increase
- Daily ingest rates grow
- Recovery SLAs become more demanding

Add storage when:

- Capacity requirements increase
- Retention periods grow
- Immutable storage requirements expand

The external S3 storage platform and Flex nodes are independently scalable.

## Plan for Growth

A good design target is:

Planning Horizon | Recommendation
--- | ---
12 months | +25% BET growth
24 months | +50% BET growth
AI / Rapid Growth Environments | +75–100% BET growth

Example:

- Current BET: 1PB
- Expected growth: 50%
- Future BET: 1.5PB

Recommended design:

- 4 Flex nodes
- Size S3 storage for 1.5PB+ usable capacity

A Flex Appliance deployment starts with two nodes and is generally sized at up to 500TB BET per node. Customers should size for both capacity and recovery performance, using additional nodes to distribute workloads, improve scalability, and meet recovery objectives while scaling storage independently on the external S3 platform.

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