Hardware RAID vs software RAID
Hardware RAID runs on a dedicated controller with its own processor and cache, offloading parity from the CPU and often adding battery-backed write cache. Software RAID (mdadm, ZFS, Storage Spaces) runs on the host CPU with no extra card and no vendor lock to a specific controller.
A hardware RAID controller presents a single logical volume to the OS and handles parity, rebuilds, and caching itself. With a battery or flash-backed write cache, it can safely acknowledge writes before they hit disk, which speeds parity RAID. The tradeoff is cost, and the fact that a failed controller may need a compatible replacement to read the array.
Software RAID moves that work to the host CPU. Modern CPUs handle parity easily, and ZFS adds checksums, snapshots, and self-healing that hardware RAID does not provide. The array is portable across machines because it is not tied to a proprietary controller. The cost is CPU cycles and, for safe write caching, careful use of a power-loss-protected SSD for the log device.
When buying, note that many servers ship with an HBA in IT mode (pass-through) rather than a RAID card, which is exactly what ZFS and mdadm want. If you need hardware RAID, confirm the exact controller model and whether the cache battery or capacitor is present and healthy, since refurb cards often arrive with dead batteries.
Related
More in Storage
- NVMe: Non-Volatile Memory ExpressNVMe is a storage protocol that lets SSDs talk directly to the CPU over PCIe lanes instead of the older SATA or SAS controller path. It cuts latency and pushes millions of IOPS, far beyond what SATA SSDs deliver.
- SAS vs SATA drivesSAS and SATA are two drive interfaces. SAS-3 runs at 12 Gbps with dual ports, full-duplex signaling, and better error handling for enterprise arrays; SATA III runs at 6 Gbps, single port, half-duplex, and costs less per gigabyte.
- U.2 and U.3 drive form factorsU.2 and U.3 are 2.5-inch enterprise SSD form factors that carry NVMe over PCIe. U.3 uses the newer SFF-TA-1001 connector so one tri-mode backplane bay accepts NVMe, SAS, or SATA; U.2 bays are wired for NVMe or SATA only.
- RAID levels (0, 1, 5, 6, 10)RAID combines drives for speed, redundancy, or both. RAID 0 stripes with no protection, RAID 1 mirrors, RAID 5 uses single parity (survives one drive loss), RAID 6 uses double parity (survives two), and RAID 10 mirrors then stripes for speed plus redundancy.
- DWPD: Drive Writes Per Day (SSD endurance)DWPD measures how many times an SSD's full capacity can be overwritten every day for its warranty period, usually five years. A 1.92 TB drive rated at 3 DWPD tolerates about 5.76 TB of writes per day. Higher DWPD means higher write endurance.
Need a build that gets this right? Tell us the workload and get an EXW Dalian quote the same business day.
Request a quote