HDD, SSHD, SSD or PCIe SSD

Hard disk drives have been the primary storage devices in all computers since decades, and there were no other options since few years.

Recently, thanks to the evolution of technology, you have different: HDD (hard disk drive), SSHD (solid state hybrid drive), SSD (solid state drive) or PCIe SSD (PCI express solid state drive)?

Below you will find comparison of these technologies and their advantages and disadvantages. In the tables, we tried to include the most popular brands, and for the price, we chose Newegg’s, Amazon’s and OWC’s online stores. Some of these products are offered with a discount, but it was not taken into account for a better comparison.

HDD

The first hard disk drives were introduced in the 1956, and the evolution since has been colossal in terms of weight, size, capacity, speed and price. They are all based on magnetic heads and rigid disks with motors to rotate the disks and move the heads.

Advantages:

• Lowest price per GB compared to all other technologies, an average of $0.10
• M.A.R.T. warns if drive is in bas shape.
• You can find HDDs with twice the maximum capacity of SSDs: 8TB for a 3.5” HDD vs. 4TB for a 2.5“ SSD, but in 2.5″ form factor, 2.5″ HDDs culminate today at 3TB.

Disadvantages:

• Read and write speed very low compared to devices with flash chips, and much higher access time.
• High battery usage in laptop.
• Heats
• Noise while operating.
• If the disk falls, it can be damaged and data can be lost.
• Lower speed if capacity is saturated and the HDD has to be defragmented.

Best for: Text editing, Internet or for users that need lot of capacity they won’t use too often. Not for mission-critical applications and video games.

SSHD

The first solid-state hybrid drives were announced in 2006 by Seagate and Samsung. They combine the traditional HDD technology with the addition of a NAND flash memory as a cache. They were introduced as intermediary between HDD and SSD, with a better price and storage capacity than SSD, and higher speed than HDD.

The SSHD is made of a low storage capacity NAND flash, an a high capacity storage HDD. It uses a software that calculates, through algorithms, most used data and chooses which ones to put on the flash cache, to make therefore the most used information more responsive and accessible at faster speed.

Advantages:

• Frequently used applications or data load faster than with HDD, faster booting.
• Drives generally with higher storage capacity than SSDs.
• Price is a little higher than HDD, but a lot cheaper than SSD: an average of $0.14 per GB for SSHD vs. $0.10 per GB for HDD.

 Disadvantages:

• Same power consumption as HDD
• Low NAND flash storage capacity which means that the performance will be altered when the cache is full.
• Same heat and noise as for HDD.
• If the disk falls, drive can be damaged and data can be lost.
• Lower speed if capacity is saturated and the disk has to be defragmented.

Best for: Users who need more performance for a few applications but also a bigger storage capacity at an affordable price.

SSD

Solid-state disks do not contain any mechanics, they are made of integrated circuits assemblies storing data. The two key components of and SSD are the controller and the memory chips.

They were introduced in the 1950s using RAM technology but were not commonly used because of their inaccessible price. Flash-based SSDs where then introduced in the 1980s by Toshiba, and again with incredibly high price. In 1991, SanDisk produced an SSD with 20MB of capacity at $1,000, a ratio of $50,000 per GB.

SSD’s price is much cheaper these days, with an average price of $0.80 per GB, but it is eight times more expensive than a traditional HDD. Price will keep falling with the coming 3D NAND 32 layer, enabling a 2.5” to have 10TB in 2016, and TLC.

The new 3D NAND technology stacks flash cells vertically in 32 layers to achieve 256Gb MLC and 384Gb TLC die that fit within a standard package. These capacities can enable gum stick-sized SSDs with more than 3.5TB of storage and standard 2.5-inch SSDs with more than 10TB.

Advantages:

• At least five times the speed of an HDD, 560MB/s for the SSD vs. 110MB/s for the HDD.
• Since there are no mechanical components, the SSD is more durable and makes no noise.
• Shock resistant.
• It uses less power than an HDD, so you get better battery life and less heat. 2W vs. 7W for an HDD.
• Can weight up to 700g less than a traditional HDD.
• Very high responsiveness, faster booting and application loading. Average latency of 47µs for the SSD vs. 12ms for and HDD or SSHD.

Disadvantages:

• Six times the price of a traditional HDD, an average price of $0.80 per GB for SSD vs. $0.10 per GB for HDD.
• Risk of losing some memory chips during its life.

Best for: notebooks with greater battery life, and users who need to load or process constantly a lot of files and heavy applications at the same time.

PCIe SSD

The PCIe interface was introduced in 2003 and replaced the traditional PCI and AGP connectors because of its high speed. It is a technology on constant development since its creation, getting faster with every new version.

A PCIe SSD is a solid state drive where the flash memories are assembled directly onto the PCIe card. It can handle up to six times the speed of 6Gb SATA. PCIe 2.0 handles a simple bandwidth of 64Gb/s and a bi-directional bandwidth of up to 128Gb/s when SATA culminates at 6Gb/s.

PCIe SSD are very fast, and, since 2007, with the new NVM express, the performance can be tripled. NVMe is architected from the ground up for Non-Volatile Memory (NVM). It significantly improves both random and sequential performance by reducing latency, enabling high levels of parallelism, and streamlining the command set while providing support for security, end-to-end data protection, and other client and enterprise features users need. NVMe provides a standard-based approach enabling broad ecosystem adoption and PCIe SSD interoperability.

Advantages:

• Can be up to four times faster than a SATA SSD, therefore ten times faster transfer rate than a traditional HDD, 1,800MB/s for the PCIe SSD vs 560MB/s for the SSD vs. 110MB/s for the HDD.
• Better latency.
• For some models, card can be thinner than usual 2.5” drives, which helps manufacturers to build smaller and lighter computers.
• No operational noise.
• Shock resistant;
• It uses less power than an HDD, so you get better battery life and less heat. 2W vs. 7W for an HDD.
• Lighter than a traditional HDD, can weight up to 700g less than a traditional HDD.

Disadvantages:

• Very high price. An average of $1.13 per GB, 30% higher than SSD.
• No standard controller like SATA, so each vendors need to create a drive controller to emulate the drive. This can sometimes create conflict between different vendor’s devices while working at the same time.

Best for: Cloud providers, enterprises or users that need lot of performance and responsiveness for heavy applications.

The most successful technology these days is the NAND flash SSD days thanks to its performance. But because of its high price some end users prefer the SSHDs that never invade the market as few OEMs embrace them and consumers finally prefer to pay more to get all the advantages of SSDs.

And the thing is, that when you are using a traditional HDD and get a taste of an SSD, the first thing that comes to your mind is: “I need one!”

SSD price per GB is still high but is falling at a higher rate than HDD. If you need top performance and you can pay the price, then go with the PCIe NVMe SSDs.

After 65 years of existence, the HDD is still the most selling storage device but the global market is now declining. Furtermore, capacity of SSDs is growing faster than HDDs. These later wlll not diseappear in the long term but will be concentrated only on high-capacity devices for secondary storage, backup and archiving replacing tapes.