Hybrid storage is a data storage solution that combines Solid-State Drives (SSDs) and Hard Disk Drives (HDDs) in a single architecture. This combination provides high speed and relatively lower latency of SSDs along with the benefit of larger capacity and cost-effectiveness of the HDDs. The result of their merging creates a storage system that gives performance and affordability, making it suitable for computation in a wide range of needs.
In day-to-day life, we come across many systems that run on SSDs but have an HDD as additional storage. These are not to be mistaken with SSHDs. In fact, it can be called a Hybrid storage system. This has become very common nowadays to use a hybrid storage system in data centers or custom-built PCs. It is made to improve performance by using SSDs to store the system software while at the same time increasing the storage needs by going with a cheaper option that doesn’t do any injustice.
Why are Hybrid Solutions Needed?
In the modern era, where the data is multiplying exponentially, we don’t only require a faster storage space but also faster data access at the same time- often at a reasonable cost. SSDs offer exceptional performance but turn out to be far more expensive for larger capacities. HDDs, while affordable, have significantly slower data access.
Hybrid Solution is a bridge to fill this gap created by offering:
- Faster Bootup and file access time
- High-capacity storage for less critical data using the HDD portion.
- Smart data management that makes sure that frequently accessed files are in SSDs for performance.
- The combination provides a very balanced solution that can do both performance-based tasks as well as bulk storage requirements.
Also, at the same time, since high-resolution content is rising due to the advancement of GPUs such as large software packages, games, and big data that is handled in AI, even an average user requires these two things:
Speed: For faster application loading, real-time processing, and multitasking
Storage Capacity: For storage of massive data, including media and software.
SSDs alone are too constant to consider for storing terabytes of data for a normal user, while HDDs may slow down the overall performance of the system. Thus, a hybrid storage system is a much-needed requirement for meeting the performance criteria without breaking the budget.
Basics of SSDs and HDDs
To understand hybrid storage, you will need to know the foundational technologies behind building it.
An HDD is the oldest storage device that uses spinning disks having magnetic particles over it. A read/write head also moves across the platter to access the data.
An SSD, on the flip side, is a modern storage device that makes use of flash memory to store data. It has no moving parts, which makes it quieter, faster, and more reliable than HDDs.
How it combines SSD and HDD into one system
The internal structure of an SSHD contains mainly three components bound in one place. These are:
Traditional HDD components:
- Spinning Magnetic Platters for Big Storage
- Read/write head for data access
- Spindle motor to rotate the platters
Embedded NAND-based Flash (SSD component)
- There is a small amount of high-speed NAND flash memory embedded. It is typically 8GB-32GB. This storage acts as a cache for the most frequently used files and data.
Embedded Controller (Firmware Logic)
- Apart from these, there is a programmed hybrid controller chip that monitors the patterns in data access to decide which files and data to store in the SSD portion/cache.
- It moves the data from storage to cache without user intervention.
How the Controller Works?
The controller can be identified as the brain of the SSHD. Here is a breakdown of how it works.
- It analyzes the frequently accessed files and their behavior/frequency.
- It prompted the frequently used data to the SSD cache. It mostly includes OS files and commonly used applications.
- It sends the rarely accessed data back to the HDDs.
- With time, the controller learns the pattern of the user and adapts to it, optimizing speed wherever required.
Caching Algorithms used in SSHDs
The SSD portion of the SSHD cannot be addressed by the user— meaning a user can never decide what exactly to store in there. It is done by a controller with the help of some algorithms and policies.
Although manufacturers decide to keep the actual algorithm abstract, they generally follow one of these.
Least Recently Used (LRU) – It is a similar algorithm that is used in the LRU cache in the CPU. It basically says to remove the data that hasn’t been accessed for quite a long time to make room for others.
Least Frequently Used (LFU) – It is an algorithm that keeps track of how often the file is accessed. The ones that are more frequently accessed are promoted to the SSD cache, while the less frequently used file resides on the HDD.
Predictive Algorithms – Some SSHDs learn patterns in the software usage of a user. It preloads the expected files as soon as the system boots up. It exhibits AI-like behavior.
Limitations of Hybrid Storage
Hybrid storage is not as fast as SSDs but is a lot faster than HDDs. The performance gain is only limited to the caching mechanism, making it overall slower than pure SSDs. Users cannot manually choose which data to transfer to the SSD cache. The SSHDs are overall HDDs with caching mechanisms. So, it is prone to damage, and it also has limited write cycles.
We see fewer SSHDs in the market because of their increasing complexity and because SSDs are getting cheaper. In today’s world, it is easy to go for a SATA SSD with higher storage space compared to a SSHD, which makes things much more complex for the end-users.
Conclusion
Hybrid storage is a very smart compromise between SSDs with high performance and HDDs with larger capacity. The SSHDs can be faster than even pure SSDs in cases with small and frequent user needs. Combining both is a cost-effective and efficient solution, but at the same time, there are limitations too. While it does not match the speed of pure SSDs in most cases, it is an affordable intelligent storage system for general user requirements.