6.9.1 RAID

February 16th, 2026

RBAC required: bear: Physical storage configuration

RAID devices in BEAR are created a bare block devices with no file system until one is assigned to them.

Remember, RAID provides redundancy not resiliency. Even RAID levels 1 and 10 should never be considered as a backup. They provide high availability through drive fault tolerance but if the data on the array is corrupted or the array is damaged in some way, the data is lost. Always have an offline backup for important data.

This article covers the following procedures:

• RAID Levels and Disk Requirements
• Preparing for Failures
• Creating a RAID Array
• Checking a RAID Array
• Repairing a RAID Array

6.9.1.1 RAID Levels and Disk Requirements

Although RAID can be flexible about matching devices of different sizes and performance, this should never be done on a production system. Performance and storage capacity will be limited by the least performant device. The table below describes the minimum requirements for different RAID levels.

RAID Level	Disks Required	Notes
RAID0	>=2	Read and write concurrency increases with the number of disks in the array. Ideally the disks should be physically distributed among different HBAs Devices may be different sizes but performance will suffer.
RAID1	2	Slower performance but high redundancy and availability Devices must be the same size.
RAID10	>=4	Scale out with redundancy and concurrency. Devices must be the same size

BEAR will not let you create an array from different disk technology types. An array must be comprised of all NVMe, SSD, or HDD. An attempt to mix types will result in an error.

6.9.1.2 Preparing for Failures

RAID levels 1 and 10 are tolerant of device failures without downtime. RAID0 has no tolerance and a failure will destroy the data requiring a new array to be built and data recovered from the last good backup (if any).

When purchasing disks for use in RAID1/10, always allow for a reasonable failure rate over the expected life of the array. The table below is a rough guide to help plan the array sensibly ahead of time.

RAID level	Service Life	Mission Critical	Active Disks	Boxed Spares
RAID1	5 yrs	N	2	1
RAID1	5 yrs	Y	2	1
RAID1	10 yrs	N	2	1
RAID1	10 yrs	Y	2	2
RAID10	5 yrs	N	4	1
RAID10	5 yrs	Y	4	2
RAID10	5 yrs	N	6	2
RAID10	5 yrs	Y	6	3
RAID10	10 yrs	N	4	1
RAID10	10 yrs	Y	4	3
RAID10	10 yrs	N	6	2
RAID10	10 yrs	Y	6	4

6.9.1.3 Creating a RAID Array

1. Physically attach/insert the disks for the array to the host. If the host does not support hot swap devices, you may need to do this while powered down.
2. From the Admin Tools menu, select Physical Storage and activate the RAID tab.

3. Provide a Device name, select a RAID level, and highlight the desired disks for the array. Selecting an odd number of disks for RAID1/10 arrays will assign one disk to be a hot spare.

Only unused disks which are not part of any existing RAID array or file system will be shown.

4. Click Create RAID Device to start the job to build the array.

6.9.1.4 Check a RAID Array

In most cases it is not required to force a manual check of the status of a RAID array. The operating system will monitor the health actively and the know status will be available in the Health tab.

However, if you have reason to suspect a RAID array may not be healthy, you can force a full scan of the array as follows:

1. From the Admin Tools menu, select Physical Storage and activate the Defragment & Repair tab.

2. Under the Scan & Repair RAID1/10 device heading, select the RAID device you wish to scan and click Scan. The scan job will start.

Depending on the size of the array, a scan job may take several hours or even days as the integrity of mirrored block or stripe is verified.

ACHE will run a scan of a RAID1/10 array automatically each Sunday. In most cases, this is enough to maintain a healthy array or detect problems that need manual intervention.

6.9.1.5 Repairing a RAID Array

Repairing a RAID array is an online (zero downtime) operation so that application availability is maintained. However, there may be a noticeable performance impact while the operation is ongoing.

If a RAID1/10 array had a failed device, it can be replaced online (no downtime) as follows:

1. From the Admin Tools menu, select Physical Storage and activate the Defragment & Repair tab.

2. Under the Replace RAID 1/10 mirror heading, select the faulted device.

No failure details or selection option will appear for RAID arrays that are not in use for a file system.

3. From the Spare Device dropdown menu, select a compatible device for the replacement.

4. Click Replace to start the repair job. This will automatically remove the faulted device from the array and add the spare device and mirror all the data to it.