TerraMaster T6-423 with trays pulled

What is RAID? How to avoid NAS data loss.


There’s always the possibility of failure with anything in life and a storage drive is no exception. You’re more prone to failure when using mechanical drives due to all the moving parts inside the device. This is where a redundant array of inexpensive disks (RAID) comes into play and I’ll run you through what it is and why you should care.

Okay, so what is RAID?

RAID is precisely what the acronym describes. It’s the formation of the best NAS drives into a single volume. While this does not automatically provide protection, some RAID types involve the duplication of data across disks to avoid data loss in the event of a drive failure.

If a drive fails in a RAID and needs to be replaced, the stored backup data on a reserved drive could be used to recreate the storage volume, allowing you to continue as if nothing happened.

If a drive fails and it’s not part of a RAID configuration, you’ll risk losing data stored on that specific drive. If a drive fails in a RAID and needs to be replaced, the stored backup data on a reserved drive could be used to recreate the storage volume, allowing you to continue as if nothing happened.

RAID does reserve a drive or two and you will lose some of the overall capacity. Part of the storage pool reserved for storing the necessary data for recovering the volume is a worthwhile sacrifice. This is a price worth paying for the protection.

Let’s say you had a two-bay NAS. Installing two 10 TB NAS drives and calling it a day with RAID 0 will provide 20 TB of capacity for storing data. The data stored on that drive will be lost due to a mechanical failure. Using RAID 1 to mirror the drives cuts capacity to 10 TB but protects against a drive failure.

Why you should use RAID on NAS

RAID on NAS is vital. These devices can hold terabytes worth of data and you need to ensure it’s protected against drive failure. While I always recommend having more than one backup copy of data, it’s also good to have the means to recover your NAS without relying on external backups.

I’ve compiled a list of the most popular RAID configurations for NAS enclosures in the table below.

RAIDMinimum drivesTolerable drive failuresData redundancyCapacityNotes
Basic10HDD sizeNo protection.
SHR10-2VariesSynology’s custom RAID. No protection with one drive.
TRAID10-2VariesTerraMaster’s custom RAID. No protection with one drive.
020HDD sizeNo protection.
121-3HDD # -1 x smallest HDD size
531HDD # -2 x smallest HDD size
642HDD # -2 x smallest HDD size
1042+HDD # -1 x smallest HDD sizeHDDs must be an even number.
Tolerable to half the number of HDDs.

Using the above table as a guide, I recommend using either SHR on a Synology NAS, TRAID on a TerraMaster NAS, or at least RAID 1 to ensure your drives are configured to avoid data loss.


RAID 0 splits (or “stripes”) data into smaller chunks for storing on two more disks. RAID 0 provides the best read and write speeds for the disk array but fails to protect against drive loss. If you lose a drive in a RAID 0 array, you’ll lose all the stored data in the pool. I would recommend keeping multiple backups of all data if using RAID 0.


RAID 1 duplicates data across two separate drives. Capacity is cut in half but should one of the two drives fail, no data will be lost due to the full immediate backup available on the working drive. Write speeds will be slower than other RAIDs due to duplicating data.


RAID 3 uses one of the available drives to store parity information for the entire array. Think of it like a table of contents. This does hit performance as a single operation addresses all installed drives, but it’s great for data protection. RAID 3 makes more sense for single-user storage solutions.


RAID 5 (known as “disk striping with parity”) is a good alternative to RAID 0 or RAID 1. RAID 5 splits data across multiple drives and stores parity data on each drive. This is a more effective RAID type for NAS with three or more drives installed. The RAID will rebuild itself using all parity data if a drive fails.


RAID 10 combines the best of RAID 1 and RAID 0 for maximum drive loss tolerance without hitting transfer speeds too hard. At least four drives are grouped into sets of two, dividing data across the entire group. The data is then duplicated on the second drive within each set. It’s the most expensive form of RAID but provides excellent redundancy and speed.

Which drives should you use?

You can use any drive inside a NAS enclosure, but I would always advise drives designed for continuous operation. The same drives found inside desktop and laptop PCs aren’t built for reading and writing data over long periods of time. They also don’t come with the more advanced features you typically find on NAS drives.

Two great NAS drive families are Seagate IronWolf and Western Digital Red Plus. They have similar capacities, specifications, and prices.

Seagate IronWolf

Seagate IronWolf 16 TB
Seagate IronWolf 16 TB. (Source: Seagate)

I’m a big fan of Seagate’s IronWolf series of NAS hard drives. Serious about storage? The Pro range offers a few advanced extras.

Western Digital

Western Digital Red Plus 8TB
Western Digital Red Plus 8TB. (Source: Western Digital)

Very similar to the Seagate IronWolf range of drives, the Red Plus from WD is designed for NAS usage and a Pro version is available with better specs.

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