docs/source/operations/install-deploy-manage/expand-minio-deployment.rst

Expand a Distributed MinIO Deployment

minio

Table of Contents

A distributed MinIO deployment consists of 4 or more drives/volumes managed by one or more minio server process, where the processes manage pooling the compute and storage resources into a single aggregated object storage resource. Each MinIO server has a complete picture of the distributed topology, such that an application can connect to any node in the deployment and perform S3 operations.

MinIO supports expanding an existing distributed deployment by adding a new Server Pool <minio-intro-server-pool>. Each Pool expands the total available storage capacity of the cluster while maintaining the overall availability <minio-erasure-coding> of the cluster. Each Pool is its own failure domain, where the loss of one or more drives or nodes in that pool does not effect the availability of other pools in the deployment.

The procedure on this page expands an existing distributed <deploy-minio-distributed> MinIO deployment with an additional server pool.

Prerequisites

Networking and Firewalls

Each node should have full bidirectional network access to every other node in the deployment. For containerized or orchestrated infrastructures, this may require specific configuration of networking and routing components such as ingress or load balancers. Certain operating systems may also require setting firewall rules. For example, the following command explicitly opens the default MinIO server API port 9000 on servers using firewalld:

firewall-cmd --permanent --zone=public --add-port=9000/tcp
firewall-cmd --reload

All MinIO servers in the deployment must use the same listen port.

If you set a static MinIO Console <minio-console> port (e.g. :9001) you must also grant access to that port to ensure connectivity from external clients.

MinIO strongly recomends using a load balancer to manage connectivity to the cluster. The Load Balancer should use a "Least Connections" algorithm for routing requests to the MinIO deployment, since any MinIO node in the deployment can receive, route, or process client requests.

The following load balancers are known to work well with MinIO:

• NGINX
• HAProxy

Configuring firewalls or load balancers to support MinIO is out of scope for this procedure.

Sequential Hostnames

MinIO requires using expansion notation {x...y} to denote a sequential series of MinIO hosts when creating a server pool. MinIO therefore requires using sequentially-numbered hostnames to represent each minio server process in the pool.

Create the necessary DNS hostname mappings prior to starting this procedure. For example, the following hostnames would support a 4-node distributed server pool:

• minio5.example.com
• minio6.example.com
• minio7.example.com
• minio8.example.com

You can specify the entire range of hostnames using the expansion notation minio{5...8}.example.com.

Configuring DNS to support MinIO is out of scope for this procedure.

Local JBOD Storage with Sequential Mounts

Network File System Volumes Break Consistency Guarantees

MinIO's strict read-after-write and list-after-write consistency model requires local drive filesystems (xfs, ext4, etc.).

MinIO cannot provide consistency guarantees if the underlying storage volumes are NFS or a similar network-attached storage volume.

For deployments that require using network-attached storage, use NFSv4 for best results.

Minimum Drives for Erasure Code Parity

MinIO requires each pool satisfy the deployment erasure code <minio-erasure-coding> settings. Specifically the new pool topology must support a minimum of 2 x EC:N drives per erasure set <minio-ec-erasure-set>, where EC:N is the Standard <minio-ec-storage-class> parity storage class of the deployment. This requirement ensures the new server pool can satisfy the expected SLA (Service Level Agreement) of the deployment.

You can use the MinIO Erasure Code Calculator to check the Erasure Code Stripe Size (K+M) of your new pool. If the highest listed value is at least 2 x EC:N, the pool supports the deployment's erasure parity settings.

Considerations

Writing Files

MinIO does not automatically rebalance objects across the new server pools. Instead, MinIO performs new write operations to the pool with the most free storage weighted by the amount of free space on the pool divided by the free space across all available pools.

The formula to determine the probability of a write operation on a particular pool is

FreeSpaceOnPoolA/FreeSpaceOnAllPools

Consider a situation where a group of two pools has a total of 10 TiB of free space distributed as:

• Pool A has 3 TiB of free space
• Pool B has 2 TiB of free space
• Pool C has 5 TiB of free space

MinIO calculates the probability of a write operation to each of the pools as:

• Pool A: 30% chance (3TiB/10TiB)
• Pool B: 20% chance (2TiB/10TiB)
• Pool C: 50% chance (5TiB/10TiB)

In addition to the free space calculation, if a write option (with parity) would bring a drive usage above 99% or a known free inode count below 1000, MinIO does not write to the pool.

If desired, you can manually initiate a rebalance procedure with mc admin rebalance. For more about how rebalancing works, see managing objects across a deployment <minio-rebalance>.

Likewise, MinIO does not write to pools in a decommissioning process.

Homogeneous Node Configurations

MinIO strongly recommends selecting substantially similar hardware configurations for all nodes in the new server pool. Ensure the hardware (CPU, memory, motherboard, storage adapters) and software (operating system, kernel settings, system services) is consistent across all nodes in the pool.

The new pool may exhibit unpredictable performance if nodes have heterogeneous hardware or software configurations. Workloads that benefit from storing aged data on lower-cost hardware should instead deploy a dedicated "warm" or "cold" MinIO deployment and transition <minio-lifecycle-management-tiering> data to that tier.

The new server pool does not need to be substantially similar in hardware and software configuration to any existing server pool, though this may allow for simplified cluster management and more predictable performance across pools.

See deploy-minio-distributed-recommendations for more guidance on selecting hardware for MinIO deployments.

Expansion is Non-Disruptive

Adding a new server pool requires restarting all MinIO nodes in the deployment at around same time.

Capacity-Based Planning

MinIO generally recommends planning capacity such that server pool expansion <expand-minio-distributed> is only required after 2+ years of deployment uptime.

For example, consider an application suite that is estimated to produce 10TB of data per year. The current deployment is running low on free storage and therefore requires expansion to meet the ongoing storage demands of the application. The new server pool should provide at minimum

10TB + 10TB + 10TB = 30TB

MinIO recommends adding buffer storage to account for potential growth in stored data (e.g. 40TB of total usable storage). The total planned usable storage in the deployment would therefore be ~80TB. As a rule-of-thumb, more capacity initially is preferred over frequent just-in-time expansion to meet capacity requirements.

Since MinIO erasure coding <minio-erasure-coding> requires some storage for parity, the total raw storage must exceed the planned usable capacity. Consider using the MinIO Erasure Code Calculator for guidance in planning capacity around specific erasure code settings.

Recommended Operating Systems

This tutorial assumes all hosts running MinIO use a recommended Linux operating system <minio-installation-platform-support> such as RHEL8+ or Ubuntu 18.04+.

For other operating systems such as Windows or OSX, visit https://min.io/download and select the tab associated to your operating system. Follow the displayed instructions to install the MinIO server binary on each node. Defer to the OS best practices for starting MinIO as a service (e.g. not attached to the terminal/shell session).

Support for running MinIO in distributed mode on Windows hosts is experimental. Contact MinIO at hello@min.io if your infrastructure requires deployment onto Windows hosts.

Expand a Distributed MinIO Deployment

The following procedure adds a Server Pool <minio-intro-server-pool> to an existing MinIO deployment. Each Pool expands the total available storage capacity of the cluster while maintaining the overall availability <minio-erasure-coding> of the cluster.

All commands provided below use example values. Replace these values with those appropriate for your deployment.

Review the expand-minio-distributed-prereqs before starting this procedure.

1) Install the MinIO Binary on Each Node in the New Server Pool

linux

macos

2) Add TLS/SSL Certificates

3) Create the systemd Service File

4) Create the Service Environment File

Create an environment file at /etc/default/minio. The MinIO service uses this file as the source of all environment variables <minio-server-environment-variables> used by MinIO and the minio.service file.

The following examples assumes that:

• The deployment has a single server pool consisting of four MinIO server hosts with sequential hostnames.

  minio1.example.com   minio3.example.com   
  minio2.example.com   minio4.example.com   

  Each host has 4 locally attached drives with sequential mount points:

  /mnt/disk1/minio   /mnt/disk3/minio 
  /mnt/disk2/minio   /mnt/disk4/minio

• The new server pool consists of eight new MinIO hosts with sequential hostnames:

  minio5.example.com   minio9.example.com
  minio6.example.com   minio10.example.com
  minio7.example.com   minio11.example.com
  minio8.example.com   minio12.example.com

• All hosts have eight locally-attached drives with sequential mount-points:

  /mnt/disk1/minio  /mnt/disk5/minio
  /mnt/disk2/minio  /mnt/disk6/minio
  /mnt/disk3/minio  /mnt/disk7/minio
  /mnt/disk4/minio  /mnt/disk8/minio

• The deployment has a load balancer running at https://minio.example.net that manages connections across all MinIO hosts. The load balancer should not be routing requests to the new hosts at this step, but should have the necessary configuration updates planned.

Modify the example to reflect your deployment topology:

# Set the hosts and volumes MinIO uses at startup
# The command uses MinIO expansion notation {x...y} to denote a
# sequential series. 
# 
# The following example starts the MinIO server with two server pools.
#
# The space delimiter indicates a seperate server pool
#
# The second set of hostnames and volumes is the newly added pool.
# The pool has sufficient stripe size to meet the existing erasure code
# parity of the deployment (2 x EC:4)
#
# The command includes the port on which the MinIO servers listen for each
# server pool.

MINIO_VOLUMES="https://minio{1...4}.example.net:9000/mnt/disk{1...4}/minio https://minio{5...12}.example.net:9000/mnt/disk{1...8}/minio"

# Set all MinIO server options
#
# The following explicitly sets the MinIO Console listen address to
# port 9001 on all network interfaces. The default behavior is dynamic
# port selection.

MINIO_OPTS="--console-address :9001"

# Set the root username. This user has unrestricted permissions to
# perform S3 and administrative API operations on any resource in the
# deployment.
#
# Defer to your organizations requirements for superadmin user name.

MINIO_ROOT_USER=minioadmin

# Set the root password
#
# Use a long, random, unique string that meets your organizations
# requirements for passwords.

MINIO_ROOT_PASSWORD=minio-secret-key-CHANGE-ME

# Set to the URL of the load balancer for the MinIO deployment
# This value *must* match across all MinIO servers. If you do
# not have a load balancer, set this value to to any *one* of the
# MinIO hosts in the deployment as a temporary measure.
MINIO_SERVER_URL="https://minio.example.net:9000"

You may specify other environment variables <minio-server-environment-variables> or server commandline options as required by your deployment. All MinIO nodes in the deployment should include the same environment variables with the matching values.

5) Restart the MinIO Deployment with Expanded Configuration

Issue the following commands on each node simultaneously in the deployment to restart the MinIO service:

6) Next Steps

• Update any load balancers, reverse proxies, or other network control planes to route client requests to the new hosts in the MinIO distributed deployment. While MinIO automatically manages routing internally, having the control planes handle initial connection management may reduce network hops and improve efficiency.
• Review the MinIO Console <minio-console> to confirm the updated cluster topology and monitor performance.