Why there are no SSDs on PCI-Express cards anymore?

The transition from utilizing SATA ports to harnessing the benefits of PCI Express has been gradually shaping the storage landscape. However, it is uncommon to come across expansion cards of this nature serving as storage units in retail stores. This raises the question: Why are PCIe SSDs scarcely available beyond the realm of laptops?

The NVMe SSDs that employ the M.2 interface essentially operate through a PCI Express connection with up to 4 lanes, albeit utilizing a distinct connector designed for these microcards. Nevertheless, desktop PC users seeking solid-state drives have often found themselves facing a choice between the larger storage capacities offered by SATA drives for 2.5-inch bays or the enhanced speed of M.2 SATA drives. This dilemma stems from the fact that the U.2 format, which is prevalent in servers and data centers, lacks support from commercial motherboards. This is precisely where PCIe SSD drives come into play.


The only option, SSD on PCI Express cards

Technically speaking, an M.2 card is a form of PCI Express card, albeit compact in size and featuring a different physical format. However, its underlying interface is still PCI Express. In the context being discussed here, we are specifically referring to full-profile expansion cards.

Within this category, there are three distinct types of units available:

1. The first type consists of an expansion card that encompasses the entire circuitry. In such cases, the flash controller takes center stage on the board, accompanied by the flash memory chips and RAM memory used for address calculations and data caching. While they may not offer faster transfer speeds compared to conventional M.2 drives, they support more memory channels, enabling a higher number of storage chips and, consequently, greater storage capacity in terabytes.

2. The second type is an adapter designed to connect to a PCI Express x16 connector, allowing up to 4 traditional M.2 drives to be connected to a PC. It’s important to note that one of the inherent capabilities of the parallel PCI Express interface is its ability to distribute communication lines among multiple peripherals simultaneously. Some high-end motherboards even include such adapters as part of their accessory package.

3. There are also units equipped with an x8 connector that enable the installation of 2 M.2 drives.

Lastly, we have a variant of the second type that facilitates the connection of a large number of drives, albeit with a reduction in individual bandwidth. For example, there are cards available that support up to 16 M.2 drives. However, it’s important to consider that each drive will correspond to a dedicated PCI Express lane, thereby utilizing 25% of the total bandwidth.

In any case, we highly recommend visiting our comprehensive tutorial on these types of cards for a more detailed exploration of the topic.

Not all motherboards have another slot for an SSD on PCIe

Many motherboard manufacturers tend to assume that the only expansion card requiring an x16 connection is the graphics card. As a result, most consumer-grade motherboards only feature a single x16 slot, which can limit expansion options. However, if you happen to have a dual-slot model, you can utilize the extra x16 slot for expanding storage capacity.

This becomes particularly useful if you’re planning to set up a home NAS (Network Attached Storage) system. Since a dedicated graphics card is unnecessary for NAS purposes, utilizing the spare x16 slot for storage expansion makes perfect sense. If you’re repurposing an old tower PC with at least a Mini-ITX form factor, you’ll find a PCI Express x16 socket available for connecting this type of card.

However, it’s important to note that using a PCI Express SSD, whether in traditional or M.2 format, for network access is generally not recommended. The benefits of high-speed storage are diminished when the bottleneck lies in the network connection. Additionally, the cost per terabyte of storage may be significantly higher compared to alternative solutions. It’s essential to consider the specific requirements of your use case.

On the other hand, if you’re planning to set up a multimedia server to stream content to multiple devices simultaneously, having a storage expansion card that supports multiple simultaneous accesses can help prevent interruptions during streaming sessions. In such scenarios, it can be advantageous to leverage the capabilities of the spare x16 slot.