HDD RAID vs SSD RAID: Making the Right Choice

Of recent, everyone’s been talking about RAID, the various types, levels, and its advantages over single-drive storage setups. RAIDs can be built with any hard disk type, whether it’s SSD or HDD. However, the argument is, can you use SSD and HDD in the same RAID setup? Well, you can use any two or more hard drive types to set up your RAID, but it is advisable to use only one type for each RAID setup.

Understanding RAID: HDD vs SSD

An HDD RAID is a RAID level created with only HDD hard drives, while an SSD RAID is a RAID created with only SSD hard drives.

A RAID level can be created with HDDs only or SSDs only, which is the best recommendable way. Notwithstanding, you can create a RAID using HDD and SSD combined; but, when you do this, there would be many irregularities in the performance of the RAID.

Apparently, HDD and SDD, although the two commonly used hard drive types, have different interfaces and support different features. When you combine the two, read and write speeds would be greatly affected, and the overall performance of the RAID, too.

How RAID Works

RAID levels provide a distinct approach to data storage, depending on the RAID level you set up. For example, RAID 1 supports data mirroring; it mirrors your data across all hard drives used in the RAID array – so that each drive stores the same exact data copy, and in a situation where one or more of the drives in the array fails, you can still access your data from the RAID, provided there is still, at least, one good drive in the array.

Similarly, each RAID level offers some level of benefits, including redundancy and fault tolerance. RAID 5 and RAID 6 utilize data striping with dedicated parity; this allows the array to automatically rebuild when one of the drives in the array fails and is replaced with a new (good) drive.

Types of RAID Configurations

The commonly used RAID configurations, also called RAID levels, are RAID 0, RAID 1, RAID 5, and RAID 6. However, some people use nested RAIDs like RAID 10, RAID 60, and RAID 50. Each of these configurations offers distinctive data storage patterns.

RAID 0: This RAID uses data striping; it strips the data in bits and distributes the bits uniquely across the entire drives in the array – each drive saves a unique bit of the block data. For this RAID configuration, there’s no fault tolerance or redundancy; one drive failure sends everything to oblivion.
RAID 1: This RAID uses data mirroring; it mirrors the block data across all drives so that all drives have the same data stored in them. This RAID offers fault tolerance – suitable for business continuity.
RAID 5: This RAID uses data striping as in RAID 0, but adds a dedicated parity drive. The dedicated parity drive comes in handy when a drive fails in the array and is replaced with a new drive – the newly added drive will be automatically rebuilt into the array, using data from the parity drive. This RAID level supports fault tolerance and redundancy.
RAID 6: Similar to RAID 5 in all aspects, except that RAID 6 supports dual parity drives, instead of a single parity drive.

Evaluating HDD RAID and SSD RAID

The major advantage of SSDs over HDDs is speed, and the major advantage of HDDs over SDDs is “cheaper cost.” Evaluating these two hard drive types for RAID configuration means weighing their benefits and demerits.

Advantages of SSDs in RAID

Faster Speeds: Inarguably, SSDs offer better read/write speeds than HDDs. When you set up an SSD-only RAID and pair it with a high-specced host system, it can significantly outperform any HDD-based RAID configuration. Typical SSD read/write speeds are around 200-500 MBs.
Reliability & Durability: SSDs have no moving parts in their build, so they are poised to last longer than HDDs if everything is equal. Also, SSDs don’t heat up like HDDs; when HDDs heat up, they tend to perform slowly.
Power Saving: Yes, SSDs consume less power resources than HDDs; you need only about 2 to 5 watts to power an SSD, but much more than that to power an HDD.

Disadvantages of SSDs in RAID

Very Expensive: SSDs are sold costlier than HDDs; some SSDs cost twice the price of their HDD counterpart of the same storage capacity.
Data Recovery on SSD is Complex: If you ever need to recover lost data from an SSD (which is quite inevitable when you work in a data-heavy environment), the process is more tedious than when you want to recover from an HDD.
Non-Compatibility With Old RAID Controllers: Your old RAID controller hardware may not be compatible with solid-state drives (SSDs).

Advantages of HDDs in RAID

Cheaper Costs: HDDs are more cost-friendly to purchase for your RAID configuration.
More Storage Options: HDDs have bigger storage capacities than SSDs. For example, you can easily find 5TB HDDs than 5TB SSDs.
Longevity: Modern HDDs have shown strong reliability over older ones. These modern ones can last for a very long time.
Suitable for Large Scale Application: If you’re running a RAID configuration where up to 20 drives or more are required, HDD is usually the most suitable, owing to its affordability and flexibility.

Disadvantages of HDDs in RAID

Slower Performance: Not like HDDs are not fast, but compared with SSDs, they are slower in read and write speeds.
High Latency and Overheating: Another downside of HDDs is that they heat up faster when in use over a long period of time, leading to high latency and sluggish performance.
Consumes More Power: While it takes just about 5 watts to power an SSD, it takes almost 15 – 20 watts to power an HDD.

Combining SSD and HDD in RAID

Although there are people who combine SSD and HDD in a RAID configuration to achieve more speed and storage capacity, this is not the best approach if you want the best performance from your RAID. Regardless, here are some advantages of combining HDD and SSD in a RAID pool.

Pros of Mixed RAID Configurations

You may get increased speed than what you would have if you used only HDDs in the setup.
You will be saving some costs compared to when you use SSDs throughout.
There would be more space to use, thanks to the HDDs in the array.

Cons of Mixed RAID Configurations

The different speed levels provided by the HDD and SSD disks can lead to performance bottlenecks.
Managing your files and data in the mixed RAID could be complex and tedious, and the drives are different.
You may not easily find a compatible RAID controller for the mixed setup.

Challenges with Mixed RAID Setups

There are additional concerns about mixing SSD and HDD in the same RAID pool. These concerns, yet again, stress the need to use only one hard drive type for your RAIDs.

1. Unstable Hardware Performance

HDDs are fragile because they have built-in moving parts, and they may fail much earlier than the SSDs, thus, leading to a fatal data loss scenario if you’re running RAID 0.

2. Storage and Performance Imbalance

In RAIDs, the overall performance is based on the lowest disk. So, your RAID will perform at the speed of the lowest-specced hard drive in the pool.

3. More Complexity

RAIDs are quite complex, using different hard drives will only make the entire setup more daunting to manage and troubleshoot.

Recovering Data from SSD and HDD RAIDs

Whether you’re using an SSD-only RAID or an HDD-only RAID, or you combined the two, a good RAID recovery software should support both HDD and SSD recovery. However, before attempting data recovery on an SSD, you should perform a preliminary check to confirm the S.M.A.R.T status of the drive.

Of course, if you were making backups of your data saved on these drives, you can simply recover your lost files by importing the backup file. But in the absence of a backup file, DiskInternals RAID Recovery tool is an ideal tool to use; it is an intuitive data recovery solution that supports multiple RAID levels, as well as includes full support for SSD and HDD RAIDs.

Conclusion

In summary, it is advisable to use one hard drive type for your RAID configuration if you wish to achieve more efficiency and stable performance. But, if you decide to mix SSDs and HDDs, that’s still possible; however, be ready for bottlenecks and unstable performance of the RAID.

If you ever face a data loss situation, DiskInternals RAID Recovery software can save the day, thanks to its multiple features and wide support for RAID configurations and Windows OS systems.

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