What is a SSHD?

A SSHD (Solid State Hybrid Drive) is a storage device that combines a traditional spinning hard disk drive (HDD) with a solid state drive (SSD) (Feeding Trends). It aims to provide a balance of the high storage capacity of HDDs and the fast performance of SSDs.

SSHDs work by using an SSD as a cache for the most frequently accessed data. The hard disk stores the bulk of the data, while the SSD cache stores copies of the most used files and data for quicker access. The SSD can speed up boot times and launch programs faster than a traditional HDD.

SSHDs were developed to provide a compromise between cost and performance. HDDs are inexpensive but slow, while SSDs are blazing fast but costly. SSHDs offer much of the speed boost of SSDs, while keeping larger storage capacities and lower prices closer to HDDs. They aim to give users improved performance without having to sacrifice high storage space or pay a premium.

SSHD Components

SSHDs contain a combination of both a solid state drive (SSD) component and a traditional hard disk drive (HDD) component that work together to improve performance.

The SSD component is typically smaller in storage capacity, ranging from 8GB to 32GB. It utilizes NAND flash memory which offers much faster read/write speeds and access times compared to traditional HDDs. The SSD caches frequently accessed data so it can be retrieved faster.

The larger HDD component provides mass storage capacity ranging from 500GB to 2TB. It uses spinning magnetic platters to store data. While HDDs have higher latency when accessing data, they provide much lower cost per gigabyte of storage.

The SSD and HDD components work synergistically in a SSHD. The SSD stores a copy of frequently accessed data from the HDD, while the HDD provides large storage capacity. When data is requested, the SSHD first checks the SSD cache. If the data is available there, it is retrieved much faster than going to the HDD. This hybrid approach merges the speed of SSDs with the storage capacity of HDDs.

Source: SSH Architecture

Advantages of SSHDs

One of the biggest advantages of SSHDs is that they are faster than traditional HDDs. According to PCPartPicker, “SSHD benefits only kick in when the same data is repeatedly accessed.” This means that frequently accessed data will be accessed much more quickly from the SSD cache compared to a regular HDD where the read/write head needs to physically move to locate the data each time [1].

Another advantage of SSHDs is they are more affordable than SSDs. As Seagate’s whitepaper explains, SSHDs provide a performance boost over HDDs by combining the speed of flash storage with the capacity of traditional drives, delivering “hybrid affordability” [2]. For many applications where an SSD would be prohibitively expensive, an SSHD can offer a nice middle-ground.

In summary, SSHDs provide some of the best features of both HDDs and SSDs. They offer faster speeds than regular HDDs for frequently accessed data, while being more affordable than SSDs with their larger storage capacities. This makes them a versatile choice for systems looking for a balance of speed, capacity, and value.

Disadvantages of SSHDs

While SSHDs aim to provide a balance of storage capacity and speed, they also come with some downsides compared to regular HDDs and SSDs:

SSHDs have a small SSD cache, usually only 8-32GB. This limits the amount of data that can benefit from the faster SSD speeds. Once the frequently accessed data exceeds the cache size, data needs to be read from the slower HDD (DocPlayer, n.d.).

Overall, SSHDs are still slower than pure SSDs, especially for large file transfers or random data reads beyond the cache. The full SSD speeds are only realized for data within the cache. For everything else, speeds are similar to traditional HDDs (AnandTech, 2012).

Lastly, SSHDs carry a price premium over standard HDDs due to the inclusion of the SSD cache and custom algorithms. While cheaper than SSDs, they cost more than an HDD with similar overall capacity (CNET, 2020).

Use Cases

SSHDs are well-suited for certain computing use cases where a balance of storage capacity and speed is ideal. Some of the most common use cases for SSHDs include:

Budget gaming builds – Gamers on a budget can benefit from SSHDs, since the flash cache helps improve load times and performance for frequently accessed games and levels. SSHDs provide more bang for the buck compared to traditional HDDs in gaming rigs. https://www.ssh.com/academy/ssh/sshd

General use computers – For day-to-day home and office tasks like web browsing, document editing, email, etc., SSHDs offer a nice blend of capacity and responsiveness. The flash cache speeds up boot times and access to everyday applications. SSHDs can keep costs down for general computing needs. https://locall.host/is-ssh-sshd/

Upgrading older systems – Older computers can get a new lease on life with a SSHD upgrade. Popping in a SSHD allows you to take advantage of unused capacity while benefiting from faster load times. It’s an easy and affordable way to breathe new life into aging machines. https://unix.stackexchange.com/questions/350284/is-sshd-necessary-for-personal-desktop-use

Popular SSHD Models

There are several popular SSHD models on the market from major hard drive manufacturers:

Seagate FireCuda – Seagate’s FireCuda line combines a standard hard drive with 8GB or more of solid state flash memory acting as a cache. Models include the FireCuda 2.5-inch drives for laptops and the 3.5-inch FireCuda drives for desktops. FireCuda drives come in various capacities from 500GB to 2TB.

WD Black2 – Western Digital’s Black2 line were 2.5-inch dual-drive SSHDs with a 120GB SSD paired with a 1TB hard drive. They provided fast solid state performance for commonly accessed files and programs while maintaining overall large storage capacity. The Black2 line has since been discontinued.

Toshiba MQ01ABD – Toshiba’s MQ01ABD SSHDs are primarily designed for laptops. They range from 5400 RPM drives with 8GB of NAND flash to 7200 RPM drives with 32GB of flash. Capacities range from 500GB to 1TB for their 2.5-inch form factor.

SSHD Cache and Algorithms

The speed boost of an SSHD comes from its integrated solid state cache, which stores frequently accessed data. The size of the solid state cache typically ranges from 8GB to 32GB on most SSHD models 1.

The caching algorithms on an SSHD work by identifying frequently accessed files like boot files, applications, games, and documents, and copying those files from the hard disk drive to the faster solid state cache. This helps speed up access to commonly used data 1.

SSHDs use proprietary algorithms from manufacturers like Seagate and Western Digital to manage the cache. These algorithms monitor data access patterns and make decisions on what data should be cached based on frequency of use, access time, and other predictive factors 2, 3. The goal is to cache the most relevant data to optimize performance.

Installation and Setup

Installing and setting up an SSHD typically involves a few key steps:

First, install the SSHD software packages on your operating system. On Linux, this usually involves running a command like sudo apt install openssh-server to install OpenSSH. On Windows, you may need to enable the SSHD Windows feature.

Next, configure the SSHD by editing the configuration file, usually located at /etc/ssh/sshd_config on Linux/Unix systems. Make changes like enabling password authentication, setting the listening port, etc.

You’ll also need to set up user accounts and permissions so people can log in. On Linux, SSHD uses the standard user accounts and permissions of the system.

For security, consider enabling key-based authentication and disabling password login. You can generate SSH keys using ssh-keygen and distribute the public keys to users.

Partitioning disks and file systems is not strictly required for SSHD installation, but can help separate and protect SSHD files from the rest of the system if desired.

For performance optimizations, consider tuning parameters like MaxSessions in sshd_config to allow more concurrent connections. Reduce unnecessary DNS lookups by setting UseDNS no. Increase the protocol version to 2 for faster operations.

After making config changes, restart the SSHD service to load the new settings. Test connecting to validate that the SSHD is functioning properly before opening it up more widely.

Keeping SSHD software updated and regularly reviewing configurations and logs will ensure it remains securely installed and optimized for your use case.

Lifespan and Reliability

SSHDs aim to provide the best of both worlds when it comes to lifespan and reliability compared to traditional HDDs and SSDs. According to one analysis, the average annual failure rate for SSHDs is around 1.5%, which is lower than HDDs at around 2% but higher than SSDs which tend to be around 1% or less [1].

The hybrid design of SSHDs provides some benefits over HDDs in terms of lifespan. The SSD cache acts as a buffer and absorbs some of the mechanical wear and tear that HDDs experience over time with constant reading and writing. However, SSHDs still rely primarily on physical spinning platters which have moving parts that can fail. So while they may last slightly longer than an HDD, the lifespan is still limited compared to SSDs which have no moving parts.

Overall, SSHD reliability and lifespan lands somewhere in between HDDs and SSDs. They tend to last longer and fail less often than traditional HDDs, but not quite as long or as reliably as pure SSDs. For many general computing uses the lifespan of a quality SSHD should suffice, but for mission critical data or systems that need maximum reliability, SSDs are still the better option.[2]

The Future of SSHDs

SSHDs are declining in popularity and seeing reduced market share as SSD prices continue to fall. SSDs offer superior performance and have become much more affordable in recent years, making them a better value over SSHDs for many consumers.

While SSHDs provide a performance boost over traditional hard drives, they still can’t match the speeds of full SSDs. As SSD prices drop, the speed and cost advantage of SSHDs diminishes. Many experts predict the SSHD market share will continue shrinking as SSD adoption grows. SSHD Technology: Trends, Innovations, and Tips.

However, development continues on new hybrid drive technologies that may breathe new life into the SSHD concept. Some emerging designs combine an SSD cache with multiple platters rather than just one hard drive platter. There is also research into more advanced algorithms to further optimize data placement and caching. But these next-gen SSHDs still face stiff competition from ever-improving SSDs. Only time will tell if they can carve out a sustainable niche. Hot Swap 7.2K SAS drives in a RAID5.