Which is better for you, SSD or HDD?

 

Choosing the right storage is more than just comparing capacity and cost. The type of storage your computer uses is important for performance, including power consumption and reliability. Solid-state drives (SSDS) and hard disk drives (HDDS) are the two main storage options to consider. This is a quick guide to the best use of each method and how to compare.

SSD and HDD: speed

What makes SSDS an increasingly popular choice is their speed. In general, SSDS are faster than HDDS because they use circuits and have no physical moving parts. This reduces wait time at startup and reduces latency when opening applications or performing heavy computing tasks. These faster speeds provide performance benefits in several ways, such as when logging in and waiting for applications and services to start, or when performing memory-intensive tasks such as copying large files. With HDDS, performance degrades significantly, while SSDS can continue to handle other tasks. Speed is also affected by the interfaces used in SSDS and HDDS, which connect to the rest of the computer system as data is transferred back and forth. You've probably heard of these interfaces -- SATA and PCI Express (PCIe). SATA is an older, slower, legacy technology, while PCIe is newer and faster. SSDS with PCIe interfaces are generally much faster than HDDS with SATA because PCIe contains more channels for transferring data. Think of it as the number of cars that can drive on a single-lane country road compared to a four-lane highway.

SSD and HDD: Durability

The amount of write wear on NAND SSDS depends in part on the state of the data already on the drive, because data is written as pages but erased as blocks. When sequential data is written to a relatively new SSD, it is efficient to write data to successive free pages on the drive. However, when small pieces of data need to be updated (such as modifying a document or value), the old data is read into memory, modified, and then rewritten to a new page on disk. Old pages containing deprecated data are marked as invalid. When free pages are no longer available, these "invalid" pages are freed for use in a background process called "defragmentation" or "wear-leveling." All existing valid pages in a given block must first be copied to other free locations on the drive so that the original block contains only invalid, deprecated pages. The original block can then be erased to free up space for writing new data. Internal NAND housekeeping (such as wear-leveling) results in write magnification, where the total internal write on the SSD is greater than the write required to simply put new data on the drive. Since each write slightly degrades the performance of a single NAND cell, write amplification is the primary cause of wear. The built-in process helps the NAND SSD evenly distribute wear throughout the drive. But most importantly, writing heavy workloads (especially random writes) can cause NAND SSDS to wear out faster than other input/output (I/O) modes because they result in greater write magnification.

Head to head comparison: SSD and HDD

In terms of capacity, SSDS for computers range from 120GB to 30.72TB, while HDDS range from 250GB to 20TB. HDDS rank high in terms of cost per unit of capacity, but as SSD prices fall, this will no longer be a differentiating factor for HDDS. With SSDS, however, you can do more work per server, reducing the number of devices deployed and getting the same output as HDDS. SSDS typically use less power and result in longer battery life because data access is faster and devices idle more frequently. By spinning the disk, HDDS require more power to start up than SSDS.

SSDS offer cost savings compared to HDDS

It is well known that SSDS perform significantly better than HDDS. Almost as well known is the reliability advantage of SSDS. Given these built-in advantages, SSDS do not require replication to improve performance, and they generally require less replication to improve reliability. The higher performance of SSDS also facilitates more efficient data reduction methods compared to HDDS. Data reduction is the ratio of the host data stored to the physical storage required; A ratio of 50% is equivalent to a 2:1 data reduction ratio. Since data reduction allows the user to store more data than on physical hardware, it increases effective capacity. Compression and deduplication techniques can greatly reduce the amount of raw storage required to meet the "available capacity" requirement.

Modern algorithms have been optimized for SSDS to leverage their performance to achieve high data reduction rates (DRR) while providing high application performance. For example, Facebook's Zstandard compression algorithm enables compression and decompression much faster than HDDS can read/write, thus allowing real-time use of the algorithm on SSDS. 2 Another example is VMware vSAN, which only provides compression and deduplication in an all-flash configuration.