A redundant array of independent disks (RAID) allows high levels of storage reliability. RAID is not a backup solution. It is used to improve disk I/O (performance) and reliability of your server or workstation. A RAID can be deployed using both software and hardware.
Below is a quick comparison of hardware vs software RAID.
| Feature | Software RAID | Hardware RAID |
|---|---|---|
| Cost: Software RAID is part of OS, so no need to spend extract money. |
Low | High |
| Complexity: The software RAID works on partition level and it can sometime increase complexity if you mix different partitions and hardware RAID. |
Medium to high | Low |
| Write back caching (BBU): The software RAID cannot add a battery. Hardware RAID can run in write-back mode if it has a BBU installed. With BBU pending writes are not lost on a power failure. |
No | Yes |
| Performance: With the software based RAID0 and RAID1 performance is negligible. However, performance goes down when you use parity-based arrays and/or several arrays at the same time. The performance of a software-based array is dependent on the server CPU performance and current load. |
Depend upon usage | High |
| Overheads (CPU, RAM etc): The software RAID must use server’s CPU and RAM for RAID software. The more hard drives means more CPU cycle will go to software RAID instead of your Apache / Postfix or MySQL server. |
Depend upon usage | No |
| Disk hot swapping: It means replacing hard disk without shutting down the server. Many RAID controller supports disk hot swapping. |
No | Yes |
| Hot spare support: A hard disk is physically installed in the array which stays inactive until an active drive fails, when the system automatically replaces the failed drive with the spare, rebuilding the array with the spare hard disk included. |
Yes | Yes |
| /boot partition: It is hard to make fail over with software RAID if /boot fails while booting the server. This can result into unexpected errors and data loss. However, LILO and FreeBSD loader can get around this problem too. |
No | Yes |
| Open source factor: *BSD / OpenSolaris and Linux RAID software drivers are open source. It means more people can fix problems as compare to a closed source hardware firmware. You can move, mix and match different sizes with open source software RAID. |
Yes | No |
| Vendor lock in (open formats): See above. | No | Yes |
| Higher write throughput: Hardware RAID with BBU may offers higher write throughput. |
No | Yes |
| Faster rebuilds: Hardware RAID with BBU may offers faster rebuilds as compare to software based solution. |
No | Yes |
| Can act as a backup solution?: Both software and hardware RAID cannot protect you against human errors or system failures or viruses. Daily scheduled and off site backups of your system are highly recommended. Use tools such as rsync, rsnapshot, tar, dump, restore and others to make daily backups. |
No | No |
| Recommend usage: | +Low cost solution +Better for RAID0 or RAID1 +Single server / workstation +Perfect for home and small business users. +No vendor lock-ins |
+Do you run a mission critical cluster or setup? +Heavy database driven dynamic site +Do you want the highest performance possible? |
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