Comparing hardware RAID vs software RAID setups deals with how the storage drives in a RAID array connect to the motherboard in a server or PC, and the management of those drives.
In a hardware RAID setup, the drives connect to a special RAID controller inserted in a fast PCI-Express (PCI-e) slot in a motherboard. When storage drives are connected directly to the motherboard without a RAID controller, RAID configuration is managed by utility software in the operating system, and thus referred to as a software RAID setup.
Advantages of hardware RAID
What does a RAID controller do for a computer or server used for data backup and recovery?
- Boosts system performance for backups and restoration, especially in legacy equipment with limited processing power, by adding DRAM cache memory to the system. Translates to less strain on the system when writing backups, and less downtime when restoring data.
- Adds RAID configuration options that may otherwise be unavailable using just the motherboard—like RAID 5/6, for example, which provides one and two drive failure tolerance.
- Protection against data corruption resulting from a loss of power during the backup process. Battery backup units (BBU) or onboard Flash memory in RAID cards provide the extra fail-safes here.
- Adds system compatibility with enterprise SAS HDDs, which are designed for 24/7 operation and have extra error correcting features compared to consumer-grade SATA III HDDs.
When might software RAID be a better option?
Dedicated RAID hardware does not always provide the best solution. It depends on several factors, however.
- Modern multi-core server CPUs are powerful enough to handle backup and restoration without a lot of system strain. Gains in backup and restore performance may be unnoticeable if an additional hardware RAID card is added to the system.
- Software RAID is used exclusively in large systems (mainframes, Solaris RISC, Itanium, SAN systems) found in enterprise computing.
- SMBs using NAS devices for backup and restore purposes will find many software-RAID based options: Netgear ReadyNAS; Synology DiskStation (DS), Buffalo TeraStation, are examples.
- Not all software RAID is equal. Flexibility is the key advantage of an open source software RAID, like Linux mdadm, but may require a specialized skillset for proper administration. Windows software RAID Storage Space has a mixed reputation (yes, a euphemism) among server administrators.
- Many hypervisors, including VMware, do not offer software RAID. Hyper-V, a Microsoft property, uses Storage Space.
What is Fake RAID?
So-called Fake RAID is a name commonly applied to motherboard / BIOS RAID features that provide the bare minimum for RAID functionality as it is understood. Low-end RAID cards get lumped in to this category because they may not offer the same DRAM cache and power loss protection features found in their more expensive counterparts. Why do low end RAID cards exist? They are mostly used to boot multiple operating systems from one array of hard drives.
Hardware RAID and SSD arrays
System administrators have reported inconsistent performance for certain hardware RAID setups that use flash storage (SSD) arrays. Older RAID controllers disable the built-in fast caching functionality of the SSD that needed for efficient programming and erasing onto the drive. Most current generation RAID controllers give users the option of re-enabling SSD disk caching to alleviate this.
Having an all-flash storage array set up for RAID 5 provides substantial performance gains compared to a HDD array.
Hardware RAID vs Software RAID: Which is better?
The type of RAID best suits data backup needs will vary from system to system. Hardware RAID is more common in Windows Server environments, wherein its advantages are better realized. Software RAID is more prevalent in open source server systems, wherein its flexibility and comparative low cost of entry make it an attractive option. Both options are completely viable; answering the hardware RAID vs Software RAID question depends on assessing the IT infrastructure—the sever hardware and system administrators operating it—to determine what makes the most sense for any organization.
3 comments
[…] About Hardware RAID and Software RAID. […]
You should look at zfs for Linux. It offers RAID, and mirror protection + parity checking with data error healing
Just because you purchase a controller it may not be HD raid. How can one tell by looking at the specs?