Hardware RAID Vs Software RAID Comparison - A Detailed Explanation
RAID stands for Redundant Array of Inexpensive Disks. This is a method of improving the performance and reliability of your storage media by using multiple drives. The drives are configured, so that the data is either divided between disks to distribute load, or duplicated to ensure that it can be recovered once a disk fails. Both can also be implemented together, to obtain both benefits, although more drives will be used. Hardware RAID was the initial type of RAID available, where a specially built RAID controller handles the drives so that the processes are almost transparent to the host computer. Software RAID is a newer type of RAID where no specialized hardware is needed, and the host computer is responsible for the drives.
Obviously, hardware RAID is pricier compared to software RAID, due to the extra hardware that you need to purchase. The hardware is typically expensive, and adds a substantial amount to the cost of the whole system. On the flip side, the cheap software RAID can impair the host computer, which may result in poor performance. This is because it needs to process the data before it is written to disk, to determine where each piece of data should go. The performance hit taken by the system can vary a lot, depending on what type of RAID array you have in use. It could be very minimal, as with the case of a JBOD array. Or it can be quite substantial, especially with stripping and mirroring on multiple disks. The controller in a hardware RAID handles these operations, so that the host processor does not have to. The host processor will simply write the data, just like in a normal hard drive.
Hardware RAID offers better reliability compared to software RAID. A software RAID can be prone to data corruption, due to the fault of the RAID software or driver that is being used. A software RAID can also be affected if the host computer is heavily loaded. Heavy processing can cause some pieces of data to be delayed by a small amount of time. These delays can add up, and negate the benefits of the RAID array to some degree.
Summary:
1. Unlike software RAID, Hardware RAID requires specialized hardware to handle the drives.
2. Software RAID is considerably cheaper than hardware RAID.
3. Unlike hardware RAID, Software RAID takes up a portion of the host processor.
4. Hardware RAID is more reliable compared to software RAID.
Obviously, hardware RAID is pricier compared to software RAID, due to the extra hardware that you need to purchase. The hardware is typically expensive, and adds a substantial amount to the cost of the whole system. On the flip side, the cheap software RAID can impair the host computer, which may result in poor performance. This is because it needs to process the data before it is written to disk, to determine where each piece of data should go. The performance hit taken by the system can vary a lot, depending on what type of RAID array you have in use. It could be very minimal, as with the case of a JBOD array. Or it can be quite substantial, especially with stripping and mirroring on multiple disks. The controller in a hardware RAID handles these operations, so that the host processor does not have to. The host processor will simply write the data, just like in a normal hard drive.
Hardware RAID offers better reliability compared to software RAID. A software RAID can be prone to data corruption, due to the fault of the RAID software or driver that is being used. A software RAID can also be affected if the host computer is heavily loaded. Heavy processing can cause some pieces of data to be delayed by a small amount of time. These delays can add up, and negate the benefits of the RAID array to some degree.
Summary:
1. Unlike software RAID, Hardware RAID requires specialized hardware to handle the drives.
2. Software RAID is considerably cheaper than hardware RAID.
3. Unlike hardware RAID, Software RAID takes up a portion of the host processor.
4. Hardware RAID is more reliable compared to software RAID.
Comparison: 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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