With the rapid development of technology, computer configuration has become the top concern for many when purchasing a computer. Yet, many people are still unclear about certain components, like how solid-state drives work and what their purpose is. Today, let’s take a look at what a solid-state drive (SSD) is.
Why has the solid-state drive become the preferred choice for more and more people? When choosing an SSD, have you ever been confused about whether to choose one with cache or one without? This article will dive deep into the differences between the two, helping you make an informed decision when purchasing.
What is a Solid-State Drive?
A Solid-State Drive (SSD) is a storage device primarily using NAND flash memory as permanent storage. An SSD is composed of a controller unit and storage units (FLASH chips, DRAM chips). SSDs are widely used in industrial control, video surveillance, network monitoring, network terminals, navigation devices, and many other fields.
Main Functions of SSD Cache:
- Pre-reading
- Cache writing actions
- Temporary storage of recently accessed data
Differences Between Hard Drives and Solid-State Drives (SSDs)
1. Different Definitions
- Hard Drive (HDD): Made up of one or more aluminum or glass platters.
- Solid-State Drive (SSD): A hard drive made from solid-state electronic storage chips.
2. Different Structures
- Hard Drive (HDD): An HDD has several platters stacked together. Each platter is divided into magnetic tracks, starting from “0” at the outer edge. Tracks with the same number form a “cylinder.”
- Solid-State Drive (SSD): An SSD mainly consists of a PCB (printed circuit board). Key components on this board include the controller chip. There is also a cache chip. Some low-end models not have a cache chip. Flash memory chips are used for storing data.
3. Different Shock Resistance
- Hard Drive (HDD): Since it’s a disk-based drive, data is stored in magnetic sectors. The shock resistance is poor.
- Solid-State Drive (SSD): Made using flash memory chips (like USB drives), SSDs have no moving mechanical parts. This means that even with high-speed movement, flipping, or tilting, it won’t affect normal use.
SSD Cache Types
SSD caches are mainly categorized into external DRAM, SLC Cache, and the latest HMB (Host Memory Buffer) technology.
The DRAM cache is an independent chip on the SSD PCB. The main components of the SSD include the Flash IC and Controller. Unlike these, this DRAM chip serves a similar role to the general RAM in a computer. It temporarily stores certain data to accelerate processing.
The cache allows many read and write tasks to use cached data, making them faster. Yet, like RAM, the data in the DRAM cache is cleared when the power is turned off. The device also clears data when it shuts down.
The SLC Cache is not a separate chip. It uses part of the TLC or QLC NAND Flash to act like SLC. Only 1 bit of data is written per cell. This method greatly boosts the SSD’s read and write performance.
DRAM Cache loses data when the power is off. In contrast, SLC Cache is saved in TLC NAND Flash. Hence, the data stays until it is deleted. This means it does not disappear when the power is turned off.
HMB (Host Memory Buffer) Technology uses a part of the computer’s memory as a cache for the SSD. The main advantage of HMB is that it utilizes unused resources. With modern PCs featuring increasingly larger amounts of RAM, ordinary users rarely use 100% of their available memory. HMB technology can assign a small part of this free memory to accelerate the SSD.
Another key point is that NAND flash’s I/O speed is steadily increasing, with the latest reaching up to 2400 MT/s. This allows good performance even without traditional DRAM. SSDs using HMB technology are to become mainstream in the future. Most newly released NVMe drives now support HMB, enabling it to assign part of DRAM to the SSD’s controller.
Windows allows up to 64MB of memory for HMB (Host Memory Buffer). In practice, the TiPlus 5000 series, with 512GB/1TB models, uses 16MB of HMB, while the 2TB version uses 32MB. This small memory usage, compared to systems with 8GB or more of RAM, significantly boosts SSD performance. It also enhances overall system performance. This provides great value for money.
Differences Between SSDs With and Without Cache:
- Speed Difference: SSDs with cache are much faster than those without cache. The larger the cache, the faster the speed improvement. The cache provides fast access to recently used data, allowing nearly instant retrieval when the data is needed again soon.
- Price Difference: Generally, SSDs with cache are faster and thus more expensive. For SSDs of the same capacity, those with cache are priced higher by a few dozen dollars. This cost reflects the speed improvement.
- SSD Usage Considerations: It’s important to note that SSDs have a write endurance limit, usually around 3000 P/E (Program/Erase cycles). One P/E cycle means the SSD can only be written to a certain number of times, typically around 3000 times.
- To Reduce SSD Wear: To reduce write data, avoid setting the virtual memory (page file) on the SSD. Avoid setting the download folder for large files like movies to the SSD, as it will cause frequent data writing.
How to Choose an SSD
Capacity: The right capacity depends on your storage needs. If you need to store a large amount of data, a higher-capacity SSD is more suitable. Generally, it’s recommended to choose at least 512GB. If you want to avoid frequent expansions or have larger data requirements, consider products with 1TB or 2TB of storage.
Read/Write Speed: Read/write speed is an important metric for evaluating hard drive performance. Faster read/write speeds can improve system speed and responsiveness. Generally, the faster the read speed, the quicker the application startup and file transfer will be.
Read/write speeds can generally be categorized into four tiers:
- Entry-level: Transfer speeds around 500MB/s, typically for SATA interface SSDs.
- Mid-range: Transfer speeds around 2000MB/s, mostly M.2 interface SSDs. High-end: Transfer speeds above 3000MB/s.
- Ultra-high-end: Speeds exceeding 7000MB/s, of course, at a higher price.
Interface Type: Choose a hard drive that matches your computer’s interface type to get the best performance. Common interface types are SATA, PCIe, and NVMe. Most modern motherboards support NVMe, and since NVMe SSDs are now affordable, it’s better to avoid buying SATA SSDs.
Cache Type: There are two types of solid-state drive caches. One is SLC cache, which uses TLC to simulate SLC to accelerate write speeds. Once the SLC cache is full, the transfer speed will drop dramatically. The other type is DRAM cache, which uses DRAM chips (memory chips) as cache. Due to chip cost considerations, DRAM cache is more commonly used in high-end SSDs.
The cache in a solid-state drive helps balance the speed difference between fast and slow devices. It can improve the read and write performance and stability of an SSD. Yet, a larger cache isn’t always better; it depends on how well the controller and flash memory chips work together.
When buying a solid-state drive, it’s important to choose a trusted brand and a reasonable price. Well-known brands usually offer better quality and customer service. Price matters too, so pick one that fits your needs and budget. Brands like Samsung, Micron, Western Digital, Kingston, Silicon Power, Crucial, and Kioxia are reliable and recommended.
SSD cache technology is improving quickly. DRAM, SLC Cache, and HMB technologies all boost SSD performance. Manufacturers use these technologies alone or together, depending on the product. Users can choose the best product based on their needs and budget.