Understanding vSAN Redundancy Levels#
Overview#
Key Points
- N+1 / RF2 (default) maintains 2 copies of every data block and can survive one simultaneous node failure. N+1 provides robust protection suitable for most production environments.
- N+2 / RF3 maintains 3 copies of every data block and can survive two simultaneous failures.
- Redundancy is configured per system and applies per vSAN tier.
VergeOS vSAN supports configurable redundancy levels — also known as Replication Factors (RF) — that determine how many copies of each data block are maintained across the system. Choosing the right level is a balance between fault tolerance, storage overhead, and infrastructure cost.
N+1 Redundancy (RF2)#
N+1 redundancy maintains 2 copies of every data block in the vSAN. This allows a cluster to survive one simultaneous failure — either a node failure or drive failures within a single node.
| Requirement | Detail |
|---|---|
| Minimum Nodes | 2 controller nodes |
| Copies of Data | 2 |
| Storage Overhead | ~2x (before deduplication) |
When to Use N+1#
VergeOS N+1 is the default configuration and well suited for most scenarios. It provides a strong balance between capacity efficiency and fault tolerance and is appropriate for many production environments when combined with best practices for data protection such as regular snapshots and off-site data replication.
Tip
For additional protection, a Repair Server can be configured to automatically attempt to retrieve missing data blocks from a sync destination if failures exceed the configured redundancy level, potentially avoiding a full snapshot rollback.
N+2 Redundancy (RF3)#
N+2 vSAN redundancy is available for environments that have a specific requirement to maintain 3 copies of every data block and/or for a system to survive two simultaneous failures. N+2 can survive two simultaneous node failures, disk failures across two nodes, or a combination of both.
| Requirement | Detail |
|---|---|
| Minimum Nodes | 3 (all controller nodes) |
| Recommended Nodes | 5 (provides a witness node to completely avoid split-brain scenarios) |
| Copies of Data | 3 |
| Storage Overhead | ~3x (before deduplication) |
When to Use N+2#
N+2 is designed for environments with a specific requirement to withstand more than one simultaneous failure. Common scenarios include ultra-critical workloads where even the brief exposure during a rebuild is unacceptable, or remote/edge sites where failed hardware cannot be replaced quickly. In these cases, the extra infrastructure cost of N+2 may be justified.
Per-Tier Redundancy#
A failure only affects the tier where the failed drives reside. For example, in an N+2 configuration, if drives on Tier 1 fail on two nodes and a Tier 4 drive fails on a different node, the cluster remains fully operational, and no data is lost.
Configuring vSAN Redundancy Level#
Redundancy level is typically configured during system installation.
Changing a System's Redundancy Levels#
It is possible to upgrade an N+1 system to N+2 (provided the minimum node requirement is met). This transition involves a data rebalancing process.
Warning
To perform a redundancy level change, contact Verge.io Support.
Viewing Tier Redundancy Status#
To check the current redundancy configuration and status of a vSAN tier:
- Navigate to Infrastructure > vSAN Tiers from the top menu.
- Double-click the desired tier to open its dashboard.
- Locate the Status card:
- Redundancy — Displays the configured redundancy level (e.g., N+1 with 2 copies, N+2 with 3 copies).
- Redundant checkbox — Indicates whether the tier is currently meeting its configured redundancy level. This will be unchecked if any nodes or tier drives are down.
Quick Comparison#
| Feature | N+1 (RF2) | N+2 (RF3) |
|---|---|---|
| Copies of data | 2 | 3 |
| Simultaneous failures tolerated | 1 | 2 |
| Minimum controller nodes | 2 | 3 |
| Recommended nodes | 3 | 5 |
| Storage overhead (before dedup) | ~2x | ~3x |
| Default | Yes | No |
Document Information
- Last Updated: 2026-03-03
- VergeOS Version: 26.1.2