How to Use Two M.2 SSD?

SSDs have become the new norm regarding storage drives these days. They have almost replaced the old hard disk drives (HDD). While the HDDs still have their use, those who have tasted SSDs can’t have enough of them. Most PCs have a single M.2 SSDs slot, which raises the question, “how to use two M.2 SSD on your PC?”

Fortunately, having two SSDs on your PC is pretty simple. If you have multiple M.2 slots on your motherboard, you can utilize them. If you do not have various M.2 slots on your motherboard, you must procure an M.2 Slot PCIe expansion card.

In the following text, I will explain in detail whether and how you can use two M.2 SSDs on your PC.

A Refresher on M.2 SSDs

It should be noted that there are two types of M.2 SSDs:

1. NVMe
2. SATA

NVMe SSDs – The Golden Standard

NVMe SSDs utilize the PCIe protocol. A typical NVMe M.2 slot uses 4 x PCIe lanes, and its speed scales with the version of the PCIe protocol the M.2 slot conforms to.

So a Gen 3 (PCIe 3.0) M.2 NVMe SSD, such as the Samsung 970 Pro, can typically reach a maximum of 3500 MB/s transfer rate. A Gen 4 (PCIe 4.0) M.2 NVMe SSD, such as the Samsung 980 Pro, can compare a maximum of about 6500 MB/s.

Of course, whether your motherboard supports Gen 3 or Gen 4, SSDs depend upon your motherboard.

NVMe SSDs are generally the golden standard. These are the SSDs that most modern desktops and laptops come with. However, you should always consult with the technical specs of your laptop or desktop to confirm what PCIe version the M.2 slot(s) your PC conforms to.

Also Read: Can You Use a PCIe 4.0 SSD On Your Existing Motherboard?

SATA SSDs – The Weaker M.2 SSDs

M.2 SATA SSDs, use, well, the SATA protocol. SATA protocol is generally intended for installing slower Hard Disk Drives.

However, SATA also finds its use for SSDs. M.2 SATA SSDs run at the maximum transfer speed of the SATA protocol.

SATA 3 has a maximum theoretical transfer rate of 6 Gbps or 750 MB/s. In reality, SATA 3 M.2 SSDs run at a maximum transfer rate of 550 MB/s.

This is many folds slower the than the NVMe SSDs.

Also Read: How to Tell if My M.2 Slot is NVMe or SATA?

Differentiating Between M.2 SATA and M.2 NVMe SSDs

Both SSDs should have labels highlighting which protocol they use.

If they don’t, then you can tell by the key notches which protocol they conform to:

• NVMe SSDs use M Key
• SATA SSDs use B+M Key

Also Read: How to Add More M.2 SSD Slots?

So How to Use Two M.2 SSD?

Now that you understand the two protocols used for M.2 SSDs, you will be better equipped when installing two M.2 drives to your PC or when procuring an expansion.

So there are two ways to add more M.2 SSDs to Your PC:

1. Use the Built-in Motherboard M.2 Slots
2. Use a PCIe Expansion Card

1. Adding 2 SSDs on the Motherboard’s Built In Slots

The simplest way to add 2 M.2 SSDs is to use the M.2 slots built onto the motherboard.

Almost all newer motherboards come with two or more M.2 SSDs slots.

You can tell how many M.2 slots you have by consulting the spec sheet. Take, for instance, the MSI MEG B550 motherboard. This motherboard has a whopping 4 x M.2 SSDs slots:

Of course, this is overkill, but most newer motherboards generally feature multiple SSDs slots.

You can read a comprehensive article here: How Many M.2 Slots Do Motherboards Have?

Beware: Not All M.2 Slots are The Same!

It would be best to note that not all M.2 slots are the same.

Recall from earlier that a typical NVMe M.2 slot uses 4 x PCIe lanes. Your SSD will need 4 x PCIe lanes to work at its highest performance level.

On some motherboards, however, the M.2 slot may only connect to 2 x PCIe lanes. Meaning the connected NVMe SSD will only perform at half its rated performance!

Take, for example, the ASUS STRIX X470-F Gaming. This motherboard offers 2 x M.2 slots but with different lane counts. The second M.2 slot only connects to 2 PCIe lanes.

Read in Detail: How Many PCIe Lanes Does M.2 Slot?

2. Adding M.2 SSDs Using an Expansion Card

If your motherboard does not have two M.2 slots, you must procure an M.2 expansion card to add more slots.

An M.2 expansion card is a PCIe device that connects to the PCIe expansion slots on the motherboard.

Again, you need to understand multiple caveats and specifications to buy the right M.2 PCIe expansion card.

NVMe M.2 Expansion Cards Have Different Sized Connectors

The size of the connector on an M.2 expansion card depends on how many M.2 slots it has.

Again, recall that an M.2 slot intended for an NVMe SSD requires 4 x PCIe lanes.

Hence when it comes to NVMe SSDs, the following are sizes you can find about the number of slots they have:

• 1 x M.2 NVMe SSD Slot – x4 connector
• 2 x M.2 NVMe SSD Slot – x8 connector
• 4 x M.2 NVMe SSD Slot – x16 connectors

The biggest card you can find is an x16 card with 4 x NVMe slots.

Also Read: Can You Put M.2 SSD in PCIe Slot?

SATA M.2 Expansion Cards Require Fewer PCIe Lanes

A SATA M.2 SSD does NOT require x4 PCIe lanes. Since it is a slow interface, even two PCIe lanes can suffice for one SATA M.2 Slot.

Take, for instance, the following M.2 SATA SSD expansion card. It has an x4 connector, yet offers 2 x M.2 slots.

The card above can also be used for NVMe SSDs. However, an NVMe SSD installed in any of these slots would only operate at half its overall capacity – since each slot connects to only 2 lanes, and NVMe SSDs ideally require 4 each.

As such, an expansion card such as the one above is ideal for SATA SSDs but NOT for NVMe SSDs.

Also Read: Do You Need an HDD and SSD Both?

You Need to Have a Free PCIe Expansion Slot

It goes without saying that to install an M.2 expansion card, you must have a free PCIe slot on the motherboard.

So if you have an M.2 expansion card with an x4 connector, you will need an x4 PCIe slot. If you have an x16 card, you will need a slot with x16 lanes.

You must refer to the motherboard’s spec sheet to determine how many PCIe lanes each slot offers.

In reality, what may seem like a full x16 slot may only have x4 or x8 PCIe lanes.

Take, for instance, the motherboard above. If you install an x8 expansion card (2 x NVMe Slots) or an x16 expansion card (4 x NVMe M.2 Slots) on the bottom x16 slot, the card will naturally not work since the bottom x16 slot is only connected to 4 x PCIe lanes.

Read more about PCIe Lanes and Slots.

Final Words

I talked comprehensively about how to use two M.2 SSDs here. First, you must understand a bit about SSDs and their jargon to install and use two M.2 SSDs.

One of the first steps in using 2 x M.2 SSDs is to read your motherboard spec sheet. Among many other things, the motherboard spec sheet can tell you:

• How many slots does M.2 have
• Which PCIe version do the M.2 slots conform to
• Whether they support NVMe, SATA, or Both SSDs
• How many lanes a slot connects
• Whether the slot shares its lanes with another PCIe slot.

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