Solid State Drives (SSD)
There has been no change in the manufacturing technique of conventional hard disk drive platters. Conventional hard disk drive platters are metal or glass discs with a surface magnetic coating. The magnetic orientation of each bit location is changed by the read/write head to store either a binary zero or a binary one. As the disc reads the data, this head identifies the magnetic orientation of every location.
Standard SSDs Contrastingly, solid-state drives (SSDs) contain all fixed parts. They use the same solid-state memory technology as used by other flash memory types. Being limited to finite number of write (including erase) operations, algorithms have been developed for all solid-state memory to constantly spread the write operations over the entire device. The life of the SSD gets enhanced due to such “wear leveling”, but this technology carries the disadvantage of lack of longevity.
In addition to reading information more quickly, SSDs also consume less power and produce less heat. Compared to their magnetic counterparts, SSDs are known to be more reliable. They are also less susceptible to damage from heat production and physical shock. Nevertheless, the manufacturing technology of SSDs is more expensive per byte. SSDs are still not available in such high capacities to rival the upper limits of conventional hard disk drive technology.
The two broadly available categories of SSDs are:
- Volatile DRAM-based SSDs
- Non-volatile flash-based SSDs
In comparison to HDDs, flash-based SSDs with NAND memory use much less power. However, DRAM uses as much power as conventional drives. SSDs made with standard RAM modules used in desktop motherboards allow up gradation by using larger modules, leading to an overall larger SSD. SSD are considered as replacements for conventional HDDs. They are expected to perform in a similar manner to retain information across a power cycle. The speed of the HDD can be maintained or exceeded with SSDs. The issue of volatility of DRAM-based SSDs can be compensated with the addition of a backup power source, such as a battery or a capacitor. Another solution could be to keep a non-volatile backup of the drive’s data that offers no detraction from the primary storage location’s speed. Flash-based SSDs can be made faster by adding a small amount of DRAM as a cache. DRAM-based SSDs will still be faster than flash-based SSDs.
Hybrid drives, considered to be a cost-saving alternative to a standard SOD, offer a significantly greater performance than conventional HDDs. A solid-state hybrid drive and a dual-storage solution are the two implementations of hybrid drives. Both these types can benefit from solutions such as Intel’s Smart Response Technology (SRT) that informs the system about the most used and highest-valued data. A copy of such data can be loaded by the drive into the SSD portion of the hybrid drive for faster read access. Systems with random access to data cannot benefit from the hybrid drive technology. Any first-time access to the data will not be done from the flash memory, taking as long as access done from a traditional hard drive. However, consistent use results in flagging of the data by the monitoring software that leads to caching in the SSD.
Solid-State Hybrid Drive
Manufactured with a substantial amount of NAND-technology solid-state storage, the solid-state hybrid drive (SSHD) acts as a conventional HDD. The operating system treats SSHD as a single drive, and the user does not have individual access to the separate components.
Dual-drive storage solutions can also take advantage of technologies such as Intel’s SRT. However, being implemented as two separate drivers (one conventional HDD and one SSD), the data to be moved to be moved to the SSD for faster read access can be chosen manually by the user. Dual-drive systems with SSDs of the same size as the HDD can be implemented for a fuller caching scenario.