What is SSD and HDD? What to choose between SSD and HDD?
Learn about the variations between HDDs and SSDs, the numerous form factors, and how their capacities, speeds, and other characteristics compare.
Selecting the best storage involves more than just comparing capacity and price. The type of storage your computer uses affects its reliability and performance, including power usage. Hard drives and solid-state drives (SSDs) are the two main storage options to consider (HDDs). Here is a brief description of how to compare them and what each one should be used for.
What's an HDD.
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The internal HDD of a computer is used to store data. On rotating disks inside, data is kept magnetically. Reading and writing data to the disk is done via transducers on the HDD's arm. With an LP record (hard disk) and a needle on an arm, it functions similarly to how a turntable record player (transducers). To access various data, the arm moves the heads across the disk's surface.
HDDs are viewed as a legacy technology because they have been around longer than SSDs. For data that is not frequently accessible, such as backups of images, videos, or corporate data, they are typically less expensive and useful. They come in two popular form factors: 3.5 inches and 2.5 inches, which are frequently found in laptops (desktop computers).
What's an SSD.
The internal parts that give these devices their name are solid state drives, or SSDs. On integrated circuits, an SSD stores all of the data. This difference between SSDs and HDDs has numerous implications, especially in terms of space and performance. Without requiring a spinning disk, SSDs can become as compact as a postage stamp or even smaller (the M.2 form factor). They are suitable for smaller devices like 2-in-1s, convertibles, and mini laptops since they can carry various amounts of data. Access times are also much reduced by SSDs because users don't have to wait for platter rotation to start.
Although SSD prices are falling more quickly than HDD prices year over year, SSDs are still more expensive than HDDs per gigabyte (GB) and a terabyte (TB) of storage. Nevertheless, the price difference is narrowing.
Speed comparison between SSD and HDD
When logging in and waiting for apps and services to start up, as well as when carrying out storage-intensive actions like copying huge files, these higher speeds have a positive impact on performance. An SSD can continue to work on other activities while an HDD's performance substantially slows down.
The interface that connects an SSD vs. HDD to the rest of the computer system while moving data back and forth also affects speed. SATA and PCI Express are two interfaces that you may be familiar with (PCIe). PCIe is a more recent technology than SATA, which is an older, slower, legacy technology. Because PCIe has more data transmission channels than SATA, SSDs with PCIe interfaces will often be substantially faster than HDDs with SATA. Consider the difference between the number of vehicles that can travel down a one-lane country road and a four-lane freeway.
Even though no one ever complains that their computer is too fast, an HDD might occasionally be advantageous. HDDs are still a more affordable option if you need to store terabytes of data, but that is changing as SSD prices continue to drop and emerging NAND technologies raise bit densities per NAND die. Consider data as either cold or hot to simplify storage decisions for computers. The years' worth of images you wish to save on your laptop but don't look at every day or need quick access to may be considered "cold" data. HDDs might be a great, affordable option for cold data. On the other hand, "hot" data is used by companies that conduct real-time commerce, edit films and images, and require quick access to a database of files, video clips, or models, or even just run the operating system. SSDs are the perfect option when quick access to your data is crucial due to their high performance.
HDD vs. SSD: Durability
Because data is written in pages but erased in blocks, the amount of write wear to a NAND SSD is somewhat dependent on the condition of the data already on the drive. Data can be efficiently written to subsequent, unoccupied pages on a relatively new SSD when writing sequential data to the device. The old data is read into memory, changed, and then rewritten to a new page on the disk when small blocks of data need to be updated, such as updating documents or numerical values. The outdated page with the deprecated data is flagged as invalid. In a background procedure known as "defragmentation" or "wear leveling," free pages that are no longer available are released for use. A block's usable pages must first be moved to other unoccupied spaces on the drive, leaving the original block with just outdated, invalid pages. To provide room for fresh data to be written, the original block can then be deleted.
Write amplification occurs when an SSD's total internal writes exceed the writes necessary to simply write fresh data to the disk. Write amplification is caused by internal NAND housekeeping routines including wear leveling. Because each writes somewhat wears down a single NAND cell, write amplification is the main factor in wear. NAND SSDs use internal mechanisms to evenly spread wear throughout the drive. The main fact is that because write-heavy workloads (random writes in particular) result in more write amplification, NAND SSDs wear down more quickly than other input/output (I/O) patterns.
The good news is that the worst-case random write patterns are always taken into account when specifying SSD drive-level endurance. For instance, if a drive says it can write one drive's worth of data every day, it indicates that every day within the drive's warranty period, you can write at least one full drive's worth of data utilizing that random write use (typically 5 years).
SSD vs. HDD comparison head-to-head
In terms of capacity, SSDs for laptops exist in sizes ranging from 120GB to 30.72TB, whilst HDDs come in sizes ranging from 250GB to 20TB. HDDs outperform SSDs in terms of cost per capacity, however as SSD prices fall, this advantage will wane for HDDs. With SSDs, however, you can accomplish far more work per server, requiring fewer machines to be deployed to get the same output as an HDD. The outcome? The TCO is reduced with SSDs (total cost of ownership).
If data is stored as intended and in an uncorrupted state, it is said to be reliable. Due to their lack of moving parts, SSDs are often more dependable than HDDs. That's because SSDs aren't harmed by vibration or other related heat problems while they aren't in motion.
Because data access is much faster and the device is idle more often with SSDs, they often require less power and have longer battery lives. HDDs startup with a higher power need than SSDs due to their spinning drives.
Savings on SSDs versus HDDs
It is common knowledge that SSDs outperform HDDs by a wide margin. The benefit of SSDs in terms of reliability is almost as well known. SSDs don't need replication for performance, and they typically need significantly less replication for reliability because of these inherent advantages. In comparison to HDDs, higher SSD performance also favors considerably more effective data-reduction techniques. Data reduction is the ratio of the amount of host data that is stored to the amount of physical storage that is needed; a 50% ratio is comparable to a 2:1 data-reduction ratio. The resulting effective capacity is improved because data reduction enables the user to store more data than is available on the physical hardware. The amount of raw storage space needed to satisfy a "usable capacity" need can be significantly reduced thanks to compression and deduplication technologies.
Modern algorithms are designed specifically for SSDs, utilizing their speed to give great application performance while enabling a high data-reduction ratio (DRR). For instance, Facebook's Zstandard compression algorithm can decompress and compress data far more quickly than HDDs can read and write data, enabling the real-time deployment of the algorithms on SSDs. 2 Another illustration is VMware vSAN, which only provides compression and deduplication in all-flash configurations.
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