Real-World Speed Tests for Different HDD RAID Levels

This tutorial measures and illustrates the difference in speeds between RAID levels for HDD (Hard Disk Drive) RAIDs. This also provides suggestions on which RAID level to choose for your storage.

NOTE: Here’s a similar tutorial covering SSD RAIDs.

RAIDs can be formatted into different RAID “levels;” for example: RAID 0, 1, 4, 5, and 1+0. Which you choose depends upon multiple factors:

• Whether the RAID uses SSD or HDD drives
• The number of drives
• The speed you want
• Whether you want automatic data backup
• Whether you want your data protected in case a drive dies

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 has tradeoffs.

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

Recently, I purchased a four-drive OWC Thunderbay 4 HDD RAID. Along with it, I purchased SoftRAID, RAID controller software published by OWC, and four Seagate Iron Wolf Pro 16 TB hard drives. This system can be configured as RAID 0 or 1 using Apple Disk Utility, or RAID 0, 1, 4, 5, 1+0 using SoftRAID. For these tests, I used SoftRAID v8.3.

The Thunderbay was connected via Thunderbolt 3.

Here are the results 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. RAIDs with more drives will be faster, but the speed relationship between different levels remains the same.

NOTE: RAID levels can only be set or changed when the RAID is empty. If you need to change the RAID level, first copy all the data you want to keep to another location.

NOTE: These tests were run on an M2 Max Mac Studio, running macOS 15.1.1, using AJA System Test (full).

Reads are always faster than writes and adding data protection always reduces speeds and total capacity.

• RAID 0 is the fastest because all four drives are used for writing or reading data. This provides 100% of the total storage capacity of the RAID, but no protection in case a drive dies.
• RAID 1 is the slowest because it is always, regardless of the number of drives in the RAID, the speed of a single drive with the storage capacity of a single drive. Most RAID 1 units only include two drives. It is ideal when you want two exact copies of your data and speed is less important.
• RAID 4 reserves one drive for “parity data” which reduces overall speed and capacity; 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 shares parity data across all drives, also reducing overall speed and capacity. But if one drive dies, all your data is protected. RAID 5 is optimized for HDD RAIDs. This provides 75% of the total storage capacity of the RAID for a 4-drive RAID.
• RAID 1+0 reserves half your total drives (2, in the case of a 4-drive RAID) to duplicate your data. It is optimized for data recovery with excellent speed. This provides 50% of the total storage capacity of the RAID. This is ideal when you want two identical copies of the data, yet with greater capacity and faster speeds than a RAID 1.

NOTE: Protecting against drive failure is not like Time Machine or backup software. There are no versions or multiple copies of the same file. Hardware protection means that if a physical drive dies, existing data is safe. If you erase a file, hardware protection will not help you recover it.

SUMMARY

For HDD RAIDs, my recommendation is to choose RAID 5 for excellent speed with protection in case of a single drive failure. Hardware failure of spinning media is not common, but not unknown. If you need maximum speed and regularly backup your data, RAID 0 is the best choice.

EXTRA CREDIT

• Here’s a PDF containing my HDD test data and testing notes.
• This article details how the tests were performed, which was part of a detailed product review of the Thunderbay 4.

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