Protecting data with mdadm – a software RAID solution
Modern computing systems rely on RAID technology to ensure data integrity, availability, and performance. By distributing data across multiple disks in various configurations, RAID provides fault tolerance, allowing systems to continue functioning even if one or more disks fail. This redundancy is critical to prevent data loss and minimize downtime.
Moreover, RAID configurations such as striping and mirroring can significantly improve read and write performance by allowing data to be accessed in parallel from multiple disks. As data volume and importance continue to increase in today’s digital world, RAID plays a vital role in protecting, optimizing, and maintaining storage system reliability. The easiest way to do this when not using Btrfs with Oracle Linux 8 is to use a tool called mdadm.
Getting ready
mdadm is a software utility for managing and configuring software RAID arrays in Linux systems. It stands for multiple device administration and is commonly used to create, manage, monitor, and maintain RAID arrays. These arrays leverage a kernel driver called multiple device (MD). mdadm allows users to create various RAID levels, including RAID, RAID 0, RAID 1, RAID 5, RAID 6, RAID 0+1, and RAID 10, using a combination of multiple physical disks:
| Type | Description | Notes |
| RAID | Spanning | No redundancy or performance advantages. |
| RAID-0 | Striping | No redundancy, but better performance versus RAID. |
| RAID-1 | Mirroring | Mirrored redundancy, but no performance advantage in write workloads. Read workloads may improve. |
| RAID-5 | Striping with double parity | Redundancy and good performance. Can lose one disk without data loss. Recommended to use at least four disks. |
| RAID-6 | Striping with tripple parity | Redundancy and good performance. Can lose two disks without data loss. Recommended to use at least five disks. |
| RAID 0+1 | Mirroring of striped disks | Great performance, but recovering a lost disk takes a long time. This requires at least four disks. |
| RAID 10 | Striping of mirrored disks | Most expensive option, but generally considered the best for redundancy, performance, and rebuild time. This requires at least four disks. |
Table 4.2 – MD RAID options
Note
It’s not uncommon to confuse a JBOD (just a box of disks) enclosure with a RAID enclosure. JBOD is a simple disk enclosure with no hardware RAID. A RAID disk enclosure has a hardware controller that offloads all the RAID logic for the disks within the enclosure. For this example, hardware RAID is not being used, only JBOD. All the RAID logic is being performed by Oracle Linux.
mdadm is an essential tool for administrators to create, modify, and monitor RAID arrays. It allows users to add or remove disks from an existing array, perform data recovery operations, and configure various parameters such as RAID level and spare disks. With its command-line interface, mdadm provides flexibility in managing and maintaining disk redundancy and performance. It is a reliable and robust solution that optimizes storage performance, ensures data redundancy, and maintains high availability of data. mdadm is normally installed when Oracle Linux is installed.
