Solid State Hard Drives Advantages and Disadvantages
Advantages:
- Faster start-up because no spin-up is required.
- Fast random access because there is no read/write head[14]
- Low read latency times for RAM drives.[15] In applications where hard disk seeks are the limiting factor, this results in faster boot and application launch times (see Amdahl's law).[16]
- Consistent read performance because physical location of data is irrelevant for SSDs.[17]
- File fragmentation has negligible effect.
- Silent operation due to the lack of moving parts.
- Low capacity flash SSDs have a low power consumption and generate little heat when in use.
- High mechanical reliability, as the lack of moving parts almost eliminates the risk of "mechanical" failure.
- Ability to endure extreme shock, high altitude, vibration and extremes of temperature.[18][19] This makes SSDs useful for laptops, mobile computers, and devices that operate in extreme conditions (flash).[16]
- For low-capacity SSDs, lower weight and size: although size and weight per unit storage are still better for traditional hard drives, and microdrives allow up to 20 GB storage in a CompactFlash form-factor. As of 2008 SSDs up to 256 GB are lighter than hard drives of the same capacity.[18]
- Flash SSDs have twice the data density of HDDs (so far, with very recent and major developments of improving SSD densities), even up to 1TB disks[20][21] (currently more than 2TB is atypical even for HDDs)[22]). One example of this advantage is that portable devices such as a smartphone may hold as much as a typical person's desktop PC.
- Failures occur less frequently while writing/erasing data, which means there is a lower chance of irrecoverable data damage.[23]
- Defragmenting the SSD is unnecessary. Since SSDs are random access by nature and can perform parallel reads on multiple sections of the drive (as opposed to a HDD, which requires seek time for each fragment, assuming a single head assembly), a certain degree of fragmentation is actually better for reads, and wear leveling intrinsically induces fragmentation.[24] In fact, defragmenting a SSD is harmful since it adds wear to the SSD for no benefit.
Disadvantages:
- Flash-memory drives have limited lifetimes and will often wear out after 1,000,000 to 2,000,000 write cycles (1,000 to 10,000 per cell) for MLC, and up to 5,000,000 write cycles (100,000 per cell) for SLC.[26][27][28][29] Special file systems or firmware designs can mitigate this problem by spreading writes over the entire device, called wear leveling.[30]
- Wear leveling used on flash-based SSDs has security implications. For example, encryption of existing unencrypted data on flash-based SSDs cannot be performed securely due to the fact that wear leveling causes new encrypted drive sectors to be written to a physical location different from their original location—data remains unencrypted in the original physical location. It is also impossible to securely wipe files by overwriting their content on flash-based SSDs.[citation needed]
- As of early-2010, SSDs are still more expensive per gigabyte than hard drives. Whereas a normal flash drive is US$2 per gigabyte, hard drives are around US$0.10 per gigabyte for 3.5", or US$0.20 for 2.5".
- The capacity of SSDs is currently lower than that of hard drives. However, flash SSD capacity is predicted to increase rapidly, with drives of 1 TB already released for enterprise and industrial applications.[21][31][32][33][34]
- Asymmetric read vs. write performance can cause problems with certain functions where the read and write operations are expected to be completed in a similar timeframe. SSDs currently have a much slower write performance compared to their read performance.[35]
- Similarly, SSD write performance is significantly impacted by the availability of free, programmable blocks. Previously written data blocks that are no longer in use can be reclaimed by TRIM; however, even with TRIM, fewer free, programmable blocks translates into reduced performance.[36]
- As a result of wear leveling and write combining, the performance of SSDs degrades with use.[37][38]
- SATA-based SSDs generally exhibit much slower write speeds. As erase blocks on flash-based SSDs generally are quite large (e.g. 0.5 - 1 megabyte),[9] they are far slower than conventional disks during small writes (write amplification effect) and can suffer from write fragmentation.[39] Modern PCIe SSDs however have much faster write speeds than previously available.
- DRAM-based SSDs (but not flash-based SSDs) require more power than hard disks, when operating; they still use power when the computer is turned off, while hard disks do not.[40]
