Recover after Hardware Failure

MinIO deployments rely on Erasure Coding to provide built-in tolerance for multiple disk or node failures. Depending on the deployment topology and the selected erasure code parity, MinIO can tolerate the loss of up to half the drives or nodes in the deployment while maintaining read access (“read quorum”) to objects.

Single-Node Single-Drive deployments are zero-parity and depend on the underlying storage volume to provide recovery. Ensure the storage volume has the necessary resiliency settings and defer to the tools or software associated to that volume for recovery.

The following table lists the typical types of failure in a MinIO deployment and links to procedures for recovering from each:

Failure Type

Description

Drive Failure

MinIO supports hot-swapping failed drives with new healthy drives.

Node Failure

MinIO detects when a node rejoins the deployment and begins proactively healing the node shortly after it is joined back to the cluster healing data previously stored on that node.

Since MinIO can operate in a degraded state without significant performance loss, administrators can schedule hardware replacement in proportion to the rate of hardware failure. “Normal” failure rates (single drive or node failure) may allow for a more reasonable replacement timeframe, while “critical” failure rates (multiple drives or nodes) may require a faster response.

For nodes with one or more drives that are either partially failed or operating in a degraded state (increasing disk errors, SMART warnings, timeouts in MinIO logs, etc.), you can safely unmount the drive if the cluster has sufficient remaining healthy drives to maintain read and write quorum. Missing drives are less disruptive to the deployment than drives that are reliably producing read and write errors.

MinIO Professional Support

MinIO SUBNET users can log in and create a new issue related to drive or node failures. Coordination with MinIO Engineering via SUBNET can ensure successful recovery operations of production MinIO deployments, including root-cause analysis, and health diagnostics.

Community users can seek support on the MinIO Community Slack. Community Support is best-effort only and has no SLAs around responsiveness.

Drive Failure Recovery

MinIO supports hot-swapping failed drives with new healthy drives. MinIO detects and heals those drives without requiring any node or deployment-level restart. MinIO healing occurs only on the replaced drive(s) and does not typically impact deployment performance.

MinIO healing ensures consistency and correctness of all data restored onto the drive. Do not attempt to manually recover or migrate data from the failed drive onto the new healthy drive.

The following steps provide a more detailed walkthrough of drive replacement. These steps assume a MinIO deployment where each node manages drives using /etc/fstab with per-drive labels as per the documented prerequisites.

1) Unmount the failed drive(s)

Unmount each failed drive using umount. For example, the following command unmounts the drive at /dev/sdb:

umount /dev/sdb

2) Replace the failed drive(s)

Remove the failed drive(s) from the node hardware and replace it with known healthy drive(s). Replacement drives must meet the following requirements:

  • XFS formatted and empty.

  • Same drive type (e.g. HDD, SSD, NVMe).

  • Equal or greater performance.

  • Equal or greater capacity.

Using a replacement drive with greater capacity does not increase the total cluster storage. MinIO uses the smallest drive’s capacity as the ceiling for all drives in the Server Pool.

The following command formats a drive as XFS and assigns it a label to match the failed drive.

mkfs.xfs /dev/sdb -L DISK1

MinIO strongly recommends using label-based mounting to ensure consistent drive order that persists through system restarts.

3) Review and Update fstab

Review the /etc/fstab file and update as needed such that the entry for the failed disk points to the newly formatted replacement.

  • If using label-based disk assignment, ensure that each label points to the correct newly formatted disk.

  • If using UUID-based disk assignment, update the UUID for each point based on the newly formatted disk. You can use lsblk to view disk UUIDs.

For example, consider

$ cat /etc/fstab

  # <file system>  <mount point>  <type>  <options>         <dump>  <pass>
  LABEL=DISK1      /mnt/disk1     xfs     defaults,noatime  0       2
  LABEL=DISK2      /mnt/disk2     xfs     defaults,noatime  0       2
  LABEL=DISK3      /mnt/disk3     xfs     defaults,noatime  0       2
  LABEL=DISK4      /mnt/disk4     xfs     defaults,noatime  0       2

Given the previous example command, no changes are required to fstab since the replacement disk at /mnt/disk1 uses the same label DISK1 as the failed disk.

4) Remount the Replaced Drive(s)

Use mount -a to remount the drives unmounted at the beginning of this procedure:

mount -a

The command should result in remounting of all of the replaced drives.

5) Monitor MinIO for Drive Detection and Healing Status

Use mc admin console command or journalctl -u minio for systemd-managed installations to monitor the server log output after remounting drives. The output should include messages identifying each formatted and empty drive.

Use mc admin heal to monitor the overall healing status on the deployment. MinIO aggressively heals replaced drive(s) to ensure rapid recovery from the degraded state.

6) Next Steps

Monitor the cluster for any further drive failures. Some drive batches may fail in close proximity to each other. Deployments seeing higher than expected drive failure rates should schedule dedicated maintenance around replacing the known bad batch. Consider using MinIO SUBNET to coordinate with MinIO engineering around guidance for any such operations.

Node Failure Recovery

If a MinIO node suffers complete hardware failure (e.g. loss of all drives, data, etc.), the node begins healing operations once it rejoins the deployment. MinIO healing occurs only on the replaced hardware and does not typically impact deployment performance.

MinIO healing ensures consistency and correctness of all data restored onto the drive. Do not attempt to manually recover or migrate data from the failed node onto the new healthy node.

The replacement node hardware should be substantially similar to the failed node. There are no negative performance implications to using improved hardware.

The replacement drive hardware should be substantially similar to the failed drive. For example, replace a failed SSD with another SSD drive of the same capacity. While you can use drives with larger capacity, MinIO uses the smallest drive’s capacity as the ceiling for all drives in the Server Pool.

The following steps provide a more detailed walkthrough of node replacement. These steps assume a MinIO deployment where each node has a DNS hostname as per the documented prerequisites.

1) Start the Replacement Node

Ensure the new node has received all necessary security, firmware, and OS updates as per industry, regulatory, or organizational standards and requirements.

The new node software configuration must match that of the other nodes in the deployment, including but not limited to the OS and Kernel versions and configurations. Heterogeneous software configurations may result in unexpected or undesired behavior in the deployment.

2) Update Hostname for the New Node

Optional This step is only required if the replacement node has a different IP address from the failed host.

Ensure the hostname associated to the failed node now resolves to the new node.

For example, if https://minio-1.example.net previously resolved to the failed host, it should now resolve to the new host.

3) Download and Prepare the MinIO Server

Follow the deployment procedure to download and run the MinIO server using a matching configuration as all other nodes in the deployment.

  • The MinIO server version must match across all nodes

  • The MinIO service and environment file configurations must match across all nodes.

4) Rejoin the node to the deployment

Start the MinIO server process on the node and monitor the process output using mc admin console or by monitoring the MinIO service logs using journalctl -u minio for systemd managed installations.

The server output should indicate that it has detected the other nodes in the deployment and begun healing operations.

Use mc admin heal to monitor overall healing status on the deployment. MinIO aggressively heals the node to ensure rapid recovery from the degraded state.

5) Next Steps

Continue monitoring the deployment until healing completes. Deployments with persistent and repeated node failures should schedule dedicated maintenance to identify the root cause. Consider using MinIO SUBNET to coordinate with MinIO engineering around guidance for any such operations.

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