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For those who don’t know the tool: OWC makes storage and connectivity hardware, but SoftRAID is its host-based RAID software for directly attached storage. It can manage compatible internal disks and external DAS rather than requiring an OWC RAID enclosure, putting the workstation CPU and software driver in charge of the array instead of a dedicated hardware RAID controller.
Yes, other boxes may apply
SoftRAID is not restricted to OWC storage. OWC has support for third-party directly attached storage, provided the computer can see the individual drives rather than receiving one preassembled logical volume from another RAID controller. So, very much unlike Avid.
That includes internal SATA and NVMe drives plus directly attached Thunderbolt, USB, eSATA and Fibre Channel storage. A SoftRAID volume can also span more than one enclosure, with a maximum of 16 drives per volume. All participating enclosures then need to remain connected for the volume to mount normally.
NAS and SAN systems are a different animal. SoftRAID needs low-level access to the member disks, so a network appliance presenting an SMB share, NFS export or other finished network volume cannot simply be adopted into a SoftRAID array. The RAID must live on DAS first; that finished volume can subsequently be shared over the network. In short: the logo on the enclosure is not the deciding factor. Seeing the actual disks is.
Soft RAID, hard RAID
A hardware RAID system puts the RAID logic in a dedicated controller, either on an expansion card or inside the enclosure. The controller handles striping, parity and recovery, then presents the result to the operating system as a logical disk. Some controllers also provide their own cache, including protected write-back cache on suitable hardware.
SoftRAID moves that work into host software. The workstation sees the member drives, while the SoftRAID driver and host CPU perform the RAID operations. There is no proprietary RAID controller sitting between the computer and the disks wearing a tiny crown.
That changes the failure model. With hardware RAID, the array can depend on a particular controller implementation, firmware and metadata format. Replacing a failed controller may require compatible hardware. With SoftRAID, the RAID logic follows the software platform instead, although the receiving system still needs appropriate SoftRAID support and direct access to the drives. On current Macs, SoftRAID volumes can be mounted for ordinary file access without installing the SoftRAID application. Windows requires the SoftRAID driver. Full creation, monitoring and configuration remain SoftRAID functions. Software RAID is therefore not inherently “cheap hardware RAID”. It is the same broad RAID idea with the arithmetic moved to a different desk.
RAID 6: two pieces of bad news allowed
The principal addition in SoftRAID 9 is RAID 6. Like RAID 5, it stripes data across several drives and calculates parity information that can reconstruct missing data. RAID 5 carries one parity set and survives one failed drive. RAID 6 calculates two independent parity sets and can survive the loss of any two members. The minimum is four drives. SoftRAID supports up to 16 drives per volume.
With equal-capacity drives, usable RAID 6 capacity is effectively the capacity of the smallest drive multiplied by the number of drives minus two. Four 8 TB drives therefore provide roughly 16 TB before filesystem overhead, six provide roughly 32 TB, and eight provide roughly 48 TB.
The capacity efficiencies are consequently 50 percent with four drives, about 66.7 percent with six and 75 percent with eight. More spindles make the two-drive parity tax progressively less dramatic. Storage accountants may unclench one finger. But just one.
RAID 6 distributes its parity information across the array rather than assigning permanent parity duties to particular disks. That spreads both data and parity traffic across the members. Its practical attraction appears during rebuilds. A RAID 5 array has spent its only redundancy once one drive has failed; another failure during reconstruction is potentially catastrophic. RAID 6 still has another parity set available and can tolerate that second failure. It is still RAID, not backup. Lose a third required member before the array has recovered and parity has run out of rabbits. And having that third drive start clicking wakes you up faster than a rabbit from a trebuchet.
RAID 6+ moves the parity furniture
RAID 6+ is OWC’s SoftRAID-specific variation. It provides the same two-drive failure tolerance and the same basic two-drive capacity overhead as RAID 6, but OWC keeps parity on dedicated drives instead of distributing it across every member. Conceptually, it takes the dedicated-parity idea of RAID 4 and gives it dual parity.
OWC positions RAID 6+ particularly for SSD and NVMe arrays. Concentrating the parity writes on dedicated members means the remaining drives can concentrate on data, and OWC says this can sustain better performance for solid-state workloads than distributing parity writes across every disk.
OWC has not published enough independent RAID 6 versus RAID 6+ production benchmarks to turn that design claim into a universal performance figure, it is all to new for that. Whether dedicated parity wins on a particular array will depend on drives, interface bandwidth, workload and queue behaviour. Storage remains distressingly unwilling to be reduced to one large number on a box.
The macOS 27 gate
Both new RAID levels require SoftRAID 9 Premium, at least four drives and macOS 27 or later according to OWC’s current RAID documentation. Other SoftRAID levels, including RAID 0, 1, 4, 5 and 10, continue to operate on supported earlier macOS releases and Windows.
There is an awkward footnote. OWC’s Windows 9.0.0.50 changelog says RAID 6 and RAID 6+ were added, while OWC’s current product and RAID documentation says both require macOS 27. Until OWC reconciles those statements, a Windows production should not assume it can create or manage the new RAID 6 modes merely because the Windows changelog mentions them.
Arrays do not grow by feeding them disks
SoftRAID volumes can contain up to 16 drives, but an existing parity array cannot simply gain another disk and expand its capacity. To increase the member count, OWC requires the data to be backed up, the volume recreated with the new disk set and the data restored. A volume can instead be enlarged by replacing its existing drives one at a time with larger models, allowing each replacement to rebuild before moving to the next. Once all members have been replaced, the volume can be expanded into the additional capacity.
When replacing a failed member, the replacement disk must be recognised by SoftRAID and added to the volume. Rebuilding then requires the volume to be mounted with read/write access. This is the point where “we have RAID” and “we have a backup” should remain two different sentences.
One useful Windows extra
SoftRAID 9 for Windows also adds access to encrypted APFS RAID volumes through OWC’s MacDrive technology. That is separate from RAID 6, but potentially useful for production storage travelling between Mac and Windows workstations. Windows still needs the relevant SoftRAID software to mount SoftRAID volumes. On modern macOS systems, ordinary SoftRAID volume access is built into the operating-system side of the equation; management is another matter.
The result is a fairly unusual storage proposition: commodity or third-party DAS, RAID logic in software, up to 16 directly visible disks and now dual-parity options without buying a dedicated RAID controller. RAID 6+ adds a more opinionated SSD arrangement by parking parity on dedicated members.
https://www.owc.com/solutions/softraid
| Product | OWC SoftRAID 9 |
| Developer | Other World Computing |
| Storage type | Direct-attached storage; OWC and compatible third-party hardware |
| Connections | Internal SATA/NVMe, Thunderbolt, USB, eSATA, Fibre Channel and other direct-attach buses |
| RAID 6 | Distributed dual parity; minimum 4 drives; tolerates any 2 drive failures |
| RAID 6+ | Dedicated dual parity; minimum 4 drives; same two-drive fault tolerance; positioned by OWC for SSD arrays |
| Maximum volume size | 16 drives |
| RAID 6/6+ requirement | SoftRAID 9 Premium and macOS 27+ |
| Network storage | NAS and SAN cannot be members of a SoftRAID volume |
| Windows | SoftRAID driver required to mount SoftRAID volumes |
| Licence | Standard is free; Premium is an annual subscription |
| Trial | 30 days with Premium features |
| Pricing | Premium: $149.99 first year, then $79.99/year; three years included with most OWC RAID storage enclosures |
