A Spin On Solid-State Drives
February 13th, 2008A friend asked me for my brief opinion regarding solid-state drives, particularly in the event of actual reviews of these devices pouring in (such as this one by Walt Mossberg of the Wall Street Journal). For the uninitiated, these solid-state drives are drop-in replacements for conventional hard disc drives (or HDDs), but employ flash storage instead of storing data on rotating magnetic media.
While this technology may be an interesting alternative for some, I do not see SSDs denting the expansive HDD market at least over the next decade. There will be some low storage capacity markets that would be taken over by solid-state storage, such as handhelds and special-purpose laptops. SDDs differ from flash storage employed by portable devices such as digital cameras and music players in two aspects: the type of flash memory used, and the interface. Current generation SDDs use the SATA interface and have a HDD-like form factor; and are therefore designed as a drop-in replacement for conventional hard drives.
My comparative reasoning between SDD and HDD technologies, is as follows:
Conventional hard drives are a mature technology and are continually seeing impressive gains in storage density (due to better materials, advances in physics, and better recording techniques). It is a just a matter of time until we start seeing multiple terabyte storage in hard drives. With a tremendous shift in media consumption towards high-definition audio and video formats, the quantity of available storage will be a perennial question.
While they do involve moving parts, the energy usage to operate a hard drive is a tiny fraction of that used for other computer parts. In todays laptops, powering the screen consumes the most energy, although this is being mitigated by the use of LED backlighting in some newer devices. In fact, in a comparative test recently performed on the Apple Macbook Air by Ars Technica, it was seen that a solid state drive presented no significant benefit in terms of battery life, even in an LED-backlit laptop computer.
The data access time benefit from flash storage is usually mentioned, but there are two sides to this story. Flash beats HDDs when it comes to random access times (due to spin delays in HDDs). However, HDDs have far superior sequential access times than SDD storage, which is of great importance in video playback and retrieving of any sequentially placed data. Moreover, with a new breed of hybrid HDDs that employ larger flash memory caches for frequently accessed information, users would be able to benefit from the best of both worlds (with greatly improved random/sequential access times as well as higher storage capacity).
A prime disadvantage of SSDs is the limited number of rewrites to memory. This makes it mandatory to perform wear-leveling within the SSD to prevent repeated rewrites to the same sections. This issue is expected to make recovering lost data from SSDs far more difficult than is the case with HDDs.
So far, the biggest advantage that I see favoring SDDs in portable computers, is the resilience from shock and damage arising from dropping the device. Therefore, computers built for rugged use and/or harsh environments would strongly benefit from using SDDs, if the compromise on storage capacity is acceptable.
