HDD, SSD or NVMe - Which data carrier for which purpose? - TUXEDO Computers

TUXEDO Computers offers the customer a choice of different data carrier formats when putting together the components of their notebook in the configurator. The choices are HDD, SSD and NVMe. We will explain in this article what the different data carriers are like, what they do and which of these data carrier formats is most suitable for which type of data.

Hard Disk Drive

Let's first take a look at the conventional HDD, which stands for Hard Disk Drive. The term disk already reveals that it is a storage medium with mechanical parts. HDDs manage the storage of data on several magnetic disks called platters on top of each other, which are written to and read from by moving read heads.

The HDD format, which has been in production since 1956, has now reached a capacity of 20 terabytes. HDDs are usually available in 3.5 and 2.5 inch formats. Due to their design, they are more susceptible to damage than data media without moving parts. Whereas HDDs used to be connected via the IDE interface, modern HDDs transfer data via the Serial ATA interface (SATA). HDDs are comparatively cheap, especially since SSD/NVMe are still costly at higher capacities. HDDs are most suitable as a data grave today. HDDs typically have a runtime of up to five years or more. They are sold as consumer or enterprise variants. The consumer HDD is designed for frequent power on and off, while enterprise variants should run 24/7.

Solid State Drive

Solid state drives (or disks), in short SSD, were developed back in the late 70s of the last millennium, but have only been commercially available for the consumer market since 2007. Since then, they have been conquering the HDDS market thanks to their undeniable advantages. SSDs are a non-volatile flash memory, like the ones used in USB flash drives, which are much faster than HDDs. Moreover, they don't contain any moving parts, so they don't have any wear in this respect and are insensitive to shocks, jolts, and vibrations. There is also the advantage of the smaller form factor. However, the price per GByte at the beginning of 2021 was still around four times higher on average than for an HDD. 

Durability of SSDs

With the mechanics of HDDs usually failing at some point and the disk no longer boots, SSD memory cells have a limited number of write cycles from the start. This depends on the installed memory type, whereby the four types Single Level Cell (SLC), Multi Level Cell (MLC), Triple Level Cell (TLC) or Quadruple Level Cell (QLC) predominate. The following applies: The more bits a cell can store, the faster it wears out. The actual wear lies in the write and erase processes. Nevertheless, well-maintained SSDs last longer than their mechanical counterparts. Techniques like wear leveling, over provisioning and bad block management help to achieve that. A special form that is no longer very common today is the hybrid hard disk (SSHD). This is a HDD that is coupled with a small flash memory that mostly holds 8 GBytes. The SSHD automatically detects which data is often accessed and stores it on the SSD. SSDs are suitable for installing the operating system, but also accelerate any other application purpose.

The NVM Express transfer protocol

NVM Express (NVMe) stands for Non-Volatile Memory Express and is a transfer protocol for fast access to data on SSDs. Thus, the above also applies to NVMe drives, which are usually plugged directly onto the motherboard in the M.2 interface format or plugged directly into a PCIe slot and connected via the fast PCI Express. In addition, there are also NVME disks as SSF (Small Form Factor) or as 2.5" devices with a U.2 connection, which are less common. The M.2 port is used in TUXEDO notebooks.

SSD vs. NVMe

The main difference between SSD and NVMe is the speed. While SSDs are mostly connected via SATA, which uses the AHCI driver once developed for HDDs, the NVMe driver is specifically designed for SSDs with flash technology. In addition, NVMe takes advantage of the PCIe bus and its direct connection to the CPU.

What are the usual speeds?

HDDs bring up the rear when it comes to speed. They achieve typical read and write speeds of 80 – 160 MByte/s. The read and write speed for SSDs with a connection to SATA3 is up to 550 MByte/s, while an SSD with a PCIe connection achieves around 1,000 MByte/s. Good NVMe SSDs today perform around 4,000 MByte/s and more.

Despite all the differences, however, there is also one thing that all storage media have in common. They only know three states: empty, full and broken. The last two usually occur much faster than desired.