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Windows, Linux, and macOS offer a wide range of alternatives for creating software RAID data storage. However, RAID as a software solution does not make sense in some cases because the performance is less than optimal and parity information is not calculated by a dedicated processor. Additionally, it does not support hot swap – that is, the ability to replace hard drives on the fly. Hardware solutions are generally recommended for RAID (redundant array of independent disks) systems, but sometimes admins might find software RAID on their servers useful.

Software RAID in Windows

In addition to storage pools, legacy disks, spanned volumes, and striped volumes, Windows Server allows you to create a software-based RAID5 system, as well as a mirrored volume that requires two hard drives to which all information is written and from which you can boot. If you are creating a disk that spans more than one physical drive, you need to select the disks that you want to include when defining the drive type. For the configuration, use the Disk Management tool, which you launch by calling diskmgmt.msc. For software RAID in Windows Server 2019, you can also use the resilient filesystem (ReFS). Creating and managing software RAID will be similar to using NTFS, with the benefit of the higher stability of ReFS.

Setting Up Disks

After initializing, you can view and set up the volumes in Disk Manager. If you are configuring a specific storage system, such as software RAID or a storage pool, and you need to convert a hard drive, you are automatically prompted. Once the disks are established, you can set them up with logical drives. The drives, simply referred to as "Disk 0," "Disk 1," and so on, in Windows Server, can be created with the New Simple Volume option in the context menu of the free space you will be using.

If you right-click directly on the data carrier in the left pane instead of on the free space to the right, you will also see the options for a New Spanned Volume and a New Striped Volume in addition to New Mirrored Volume and New RAID-5 Volume (Figure 1).

Figure 1: You can create new volumes, including software RAID, in the Disk Management system utility.

Repairing Software RAID

If you create a volume that spans multiple drives, you can repair it from the context menu should the need arise (e.g., if one of the disks fails or you replace a disk). Windows points out in the Disk Management system utility that some follow-up work is needed for spanned volumes. In this case, the context menu for the disk displays more settings options at the bottom.

If an extended volume fails because a physical hard drive can no longer be accessed, the Repair Volume option appears, assuming that Windows finds an empty volume that can be used to repair the extended volume. If you select this menu item, Windows automatically suggests the physical drive that will be used to recover the spanned volume. If a physical hard drive of a RAID5 volume is defective, you need to replace the disk, restart Windows, and select Repair Volume from the context menu. You do not have to initialize the data carrier, but you can switch it to the online state.

If you just temporarily disconnect a physical hard drive from the system and then reconnect it, you do not need to repair the volume; rather, you "reactivate" it from the disk's context menu. However, if a physical disk in a spanned volume fails, Windows disables it in Explorer if access is no longer technically possible. Choosing Reactivate Volume (Figure 2) lets you reactivate the disk in this case (e.g., to back up the data).

Figure 2: Volumes that have been disabled by the system can be put back into operation in the Disk Management overview of disks.