Selecting the right GlusterFS volume type determines whether data stays accessible during outages, how much raw disk becomes usable capacity, and how painful recovery is after a failed disk, node, or link.
A GlusterFS volume is built from bricks that are grouped into protection sets. Replicated volumes store full copies across a replica set, while dispersed volumes use erasure coding to split data and parity across a disperse set; adding a distributed layer spreads the same protection across multiple sets to scale capacity.
The layout choice is effectively a design-time decision, since changing between replication and dispersion later usually means building a new volume and migrating data. Brick placement matters as much as the type—placing multiple bricks from the same set in a single failure domain defeats redundancy—and pure distributed layouts provide no redundancy at all.
GlusterFS volume type selection guide:
- Map each planned brick to a failure domain such as a host, rack, or site.
Replica and disperse sets should avoid placing multiple bricks from the same set in the same failure domain.
- Use replicated volumes when maximum availability is needed with a smaller node count.
Replica 2 stores two full copies (usable capacity is ~50% of raw); replica 3 stores three full copies (usable capacity is ~33% of raw).
- Use distributed replicated volumes to scale capacity while retaining replica protection.
Total brick count must be a multiple of the replica count so complete replica sets can be formed.
- Use dispersed volumes for erasure-coded redundancy with lower storage overhead.
The redundancy value is the number of brick failures tolerated per disperse set; for example, disperse 6 with redundancy 2 tolerates 2 brick failures per set.
- Use distributed dispersed volumes to scale erasure-coded storage across multiple disperse sets.
Total brick count must be a multiple of the disperse count (data + parity) so complete disperse sets can be formed.
- Use arbiter volumes to reduce split-brain risk without full replica storage cost.
Arbiter is a replica 3 layout with two data bricks plus one metadata-only arbiter brick, typically placed on a lightweight third node.
- Avoid plain distributed volumes for data that must survive a brick failure.
Pure distribution has no redundancy; losing a brick makes the files stored on it unavailable until restored from backup or recovered.
Mohd Shakir Zakaria is a cloud architect with deep roots in software development and open-source advocacy. Certified in AWS, Red Hat, VMware, ITIL, and Linux, he specializes in designing and managing robust cloud and on-premises infrastructures.
