Real-World Speed Tests for Different SSD RAID Levels

This tutorial measures and illustrates the difference in speeds between different RAID levels. These tests apply to both SSD and HDD RAIDs. It also makes clear which RAID level you should use for your storage.

RAIDs can be formatted into different RAID “levels.” For example, RAID 0, 1, 4, 5, 6 and 1+0. Which you choose balances three factors:

• Whether the RAID uses SSD or HDD drives
• The speed you want
• The protection you want in case one or two drives die

The more protection, the slower the speed and the lower the storage capacity. There’s no “right” answer, just the answer that works best for you. Like most of tech, each choice is a tradeoff.

NOTE: Here’s an article that describes each RAID level in a bit more detail.

Recently, I purchased an OWC Thunderblade. This is a 4-drive NVMe SSD RAID which can be configured into any of these RAID levels, except RAID 6. (RAID 6 is specifically designed for HDD RAIDs. It provides protection in case two HDD drives die at the same time. This is not a practical format for SSD RAIDs.)

Here are the results. Results are displayed as a percentage because actual speeds will vary based upon the number of drives, how they are connected, the speed of your computer and a few other factors. However, the relationship between these different formats will remain roughly the same.

NOTE: RAIDs with more than four drives will have faster results for RAID levels 4 and 5, but RAID 0 will always be the fastest.

(Click to see larger image)

NOTE: Red bars indicate the theoretical speeds for reading and writing. Green bars indicate actual real-world results. All RAIDS were formatted using OWC SoftRAID.

Reads are always faster than writes. And, while none of the numbers perfectly matched the theory, they were all reasonably close.

• RAID 0 is the fastest because all four drives are used for writing or reading data. To make the comparison easier, I set the speed of RAID 0 to equal 100%. This provides 100% of the total storage capacity of the RAID.
• RAID 1 is the slowest because it is always, regardless of the number of drives, the speed of a single drive. As well, this only provides the storage capacity of a single drive regardless of how many drives are in the RAID.
• RAID 4 reserves one drive for “parity data” which reduces overall speed. But if one drive dies, all your data is protected. RAID 4 is optimized for SSD RAIDs. This provides 75% of the total storage capacity of the RAID for a 4-drive RAID.
• RAID 5 also reserves one drive for “parity data” which reduces overall speed. But if one drive dies, all your data is protected. RAID 5 is optimized for HDD RAIDs; notice that it is slower than RAID 4 on this SSD RAID. This provides 75% of the total storage capacity of the RAID for a 4-drive RAID.
• RAID 1+0 reserves half your drive (2, in the case of a 4-drive RAID) for parity data. It is optimized for data recovery. This provides 50% of the total storage capacity of the RAID. This format is the fastest when you want both data redundancy and speed.

SUMMARY

For maximum speed, choose RAID 0. If you are worried about losing a drive choose RAID 4 for SSD RAIDS, or RAID 5 for HDD RAIDs, but there is a tradeoff in terms of both speed and storage capacity.

However, given the cost of SSD drives, it is cheaper to format the RAID as RAID 0, then buy an inexpensive hard drive equal to the size of the SSD RAID and backup your data every night to that stand-alone HDD.

EXTRA CREDIT

• Here’s a PDF containing a table summarizing my results, including details on how the tests were conducted.
• This article details how the tests were performed, which was part of a detailed product review of the Thunderblade.