Redundant array of independent disks (RAID) is a technique to virtualize independent disks into one or more arrays for improved performance, capability, fault tolerance, and reliability. This grouping of disks into logical arrays can be achieved through hardware or software implementation. For an overview of RAID levels, check out our recent story here at TechGenix. In this article, let’s take a detailed look into what hardware or software RAID is, including the advantages and disadvantages of each, and we’ll evaluate which of the two is better for you.
A hardware RAID is an implementation where all the disks connect to a piece of hardware called the RAID controller that’s inserted in a PCI slot in the motherboard. These RAID controllers physically control the RAID array and support all RAID levels and custom configurations. In some cases, these RAID controllers are smaller versions of computers since they come with dedicated processors to perform their roles.
The main role of a RAID controller is to manage these independent disks and present them to the computer as one or more logical units.
In a hardware implementation, there are two types of RAID controllers, namely,
- Bus-based: These controllers come with the motherboard for the most part and are used for controlling the lower-end RAID levels.
- Card-based and intelligent controllers: These are mostly for high-end systems and are typically installed in a separate box as they come with dedicated processors. Obviously, they are more expensive and more difficult to install when compared to a bus-based installation.
It’s important to note that RAID controllers score lower on flexibility. For example, a RAID controller designed for RAID 0 implementation will not work well on RAID systems designed for fault tolerance. Also, controller chips designed for IDE systems don’t work on SCSI systems, though major manufacturers like Intel develop some RAID controller versions that work well for all types of disks.
Now that we have a good idea about hardware RAID, let's see its advantages and disadvantages.
Advantages of hardware RAID
Some of the advantages of a hardware RAID are:
- Greatly improves system performance, especially in legacy systems with limited capacity for improving processing power.
- Less strenuous on the system during backup and recovery.
- Gives the flexibility to add any RAID configuration that may otherwise be hard to implement using just the motherboard.
- Protects against data loss or corruption that may occur when power is interrupted during a data backup.
- Works well across all types of drives.
- It can run in the write-back mode provided it has a battery.
Disadvantages of hardware RAID
The disadvantages of hardware RAID are:
- More expensive to implement as you have to invest in new hardware equipment.
- When the RAID controller fails, you need to replace it with a similar controller to ensure no disruptions to your work.
Thus, these are the advantages and disadvantages of a hardware RAID.
Let’s move on to the software RAID now.
Software RAID is an implementation that uses the capabilities of an operating system through a RAID software or driver to implement RAID. It requires no additional hardware.
The RAID software communicates with the disks through local interfaces and adapters and tends to have higher levels of compatibility with different systems.
Advantages of software RAID
Some of the key advantages of software RAID are:
- It is cheap to implement.
- The same RAID driver can be implemented across many systems that use the same operating system.
- Reconfiguring RAID levels is possible without any restrictions.
Disadvantages of software RAID
A software RAID comes with its share of disadvantages too.
- Tends to be slower since it shares the processing capacity of the operating system.
- Works well only on a single type of operating system, so it can't be implemented for disks that are shared by different operating systems.
- Replacing a failed disk is a complex process.
- Highly vulnerable to viruses, unprotected at boot, and creates data integrity issues due to system crashes.
Thus, these are the advantages and disadvantages of a software RAID.
So, which of the two is better?
Hardware vs. software RAID
So far, we have seen the two RAID implementations and the advantages and disadvantages of each. Now comes the important question — which of the two is better?
The answer depends on the RAID level, budget, heterogeneity of your systems, and more.
Let’s look at different scenarios to see which of the two would work well in each.
If you’re on a tight budget or if you want to explore the impact of RAID on your performance or fault tolerance, software RAID is the choice since it is way less expensive than hardware RAID and can be implemented across multiple systems.
Of course, it makes sense to have a long-term plan, too, given that software RAID comes with many limitations.
RAID 0 or 1 implementation
If you’re looking to implement RAID 0 or RAID 1 levels, there won’t be a significant difference between hardware and software RAID implementations. So, look into other constraints such as your budget and the heterogeneity of your systems to decide one over the other.
RAID 5 or 6 implementation
On the other hand, if you’re looking to implement a high-level RAID implementation such as RAID 5 or 6, hardware RAID is your best bet because it offers better performance. Also, RAID levels like RAID 10 are not supported by software, so go for hardware implementations for such custom configurations.
Heterogeneity of your systems
If all your systems run on the same operating system and if you want to implement the lower-end RAID levels, go for a software implementation. But if you have to manage disks that are shared by operating systems, hardware RAID is the way to go.
In general, a hardware RAID is better because it gives you more flexibility to configure custom RAID levels and offers better performance. It is easier to set up, replace, and manage when compared to a software RAID, and it is undoubtedly, the better choice if your budget allows it.
As we come to the end of this discussion, we’ll talk about a hardware-assisted software RAID, which is essentially a software-driven implementation but comes with additional hardware to overcome some of the problems that come with a pure software implementation. For example, RAID BIOS is integrated into the motherboard to provide redundancy when a system is turned on, to prevent the possibility of data corruption. Also, it works better across different operating systems.
Advantages of a hybrid RAID are:
- Not too expensive and is affordable for most small to medium-sized businesses.
- Gives protection against boot failures that could occur due to medium errors or even boot failures.
- Comes with a dedicated GUI to maintain RAID.
- Works well across multiple operating systems.
The disadvantages are:
- There is an additional load on the server that, in turn, could impact its performance.
- Vulnerable to viruses.
- Newer versions of operating systems may require you to regularly update your drivers.
As you can see, a hybrid RAID is not a perfect solution, but instead acts as a bridge between hardware and software implementation and works well if you’re on a limited budget and want to avoid some of the pitfalls that come with a software implementation.
Hardware RAID or software RAID? Depends on your goals
To conclude, RAID can be implemented through a dedicated RAID controller called a hardware RAID or through software or a driver called a software RAID. Both come with their share of strengths and weaknesses, so the right implementation depends on your goals, budget, nature of systems, RAID level, and other pertinent factors.
In general, though, a hardware implementation provides better performance, gives more flexibility to configure RAID levels, and works well across all systems, even if it is more expensive than a software RAID. In contrast, a hybrid RAID can strike a mid path between a pure software and hardware implementation.
Which of the two do you prefer and why? Please let us know in the comments.
More RAID levels articles
- Hackers: the New Ghosts in the Machine
- RAID 5 vs. RAID 6: When to use each level and why
- RAID 10 vs. RAID 5: When to use each level and why
- RAID 1 vs. RAID 5: When to use each level and why
- RAID 0 vs. RAID 1: When to use each level and why