For most computer users, the (magnetic) hard disk drive is the last thing they think about, that is, until it fails. With flash-based solid state drives getting more affordable, the industry is looking at a likely replacement for the HDD. Lim Yeh Ern pits the SSD against the HDD to find out how much potential it has in optimising the performance of the computing system.
Mortality rate
JUST like any machine with mechanical components, hard disk drives tend to deteriorate over time. HDDs consist of rotating, magnetically coated disks, known as platters, which are used to store data. This rotating motion of the mechanical arms results in wear and tear after long periods of usage. The operational lifespan of an HDD is typically more than three years.
A flash-based solid state drive is different. Although common flash chips have around 300,000 write cycles, the best flash chips are rated at 1,000,000 write cycles per block.
On top of that, flash SSD manufacturers employ different ways to increase the longevity of the drives. In some cases, they use a 'balancing' algorithm to monitor the number of times each disk block has been written, which greatly extends the operational lifespan of the drive.
Furthermore, these manufacturers also designed special 'wear-levelling' algorithms where once a certain percentage threshold for a given block is reached, the SSD will swap the data in that block with the data in another block that has exhibited a 'read-only-like' characteristic in the background. This reduces performance lag and avoids further wearing off of the blocks and thrashing of the disk.
Even with usage patterns of writing or reading gigabytes (GBs) per day, a flash-based SSD should last several years, depending on its capacity. Add to that the inclusion of a dynamic random access memory cache in the disk architecture, that further enhances its operational capabilities and lifespan.
Size matters
HDDs are already at a density where manufacturers are stuck at 320GB per 2.5-inch hard drive platter. We're talking about a standard-sized single platter that fits in your notebook computer, not those non-standard 2.5-inch 500GB drives with two platters appearing in USB portable pocket drives.
SSDs, on the other hand, are gaining ground at 240GB in flash chips on a 2.5-inch printed circuit board (PCB), and growing. Since an SSD is made up of a PCB, manufacturers designed a plastic enclosure which takes the same form as a standard 2.5-inch hard drive just so it fits in a standard notebook hard disk bay. Smaller form factors include the 1.8-inch and one-inch.
Reliability
IN terms of reliability, conventional HDDs pale in comparison to SSDs. The absence of mechanical arms and spinning platters is the reason behind its reliability. In demanding environments, SSDs provide the type of ruggedness needed for mobile applications.
Unlike HDDs, SSDs can withstand extreme shock and vibration with data integrity and without any danger of data loss. This feature is important in industrial applications where exposure to highly combustible materials and electromagnetic radiation is typical. The ability to deliver unnerving performance in extreme conditions also gives SSDs a vital role to play in military operations, be it in defence, aerospace or aviation application.
Speed
SOME industrial figures state that SSDs are twice as fast during bootup and 50 per cent more energy-efficient while boasting a mean time to failure (MTTF) rate of six times greater than standard HDDs.
As beautiful an electromechanical design the HDD is, it still relies on the mechanics to spin a spindle and actuate a read-and-write mechanical at speeds beyond
5,400 revolutions per minute (rpm) with an air gap less than 4,000 times the thickness of a human hair.
The extreme tolerances between the platters and the read/write heads mean that the HDD is more prone to head crashes - a term used when the read/write head makes contact with the magnetic platters resulting from something as mundane as accidentally dropping the notebook to normal wear and tear.
Sandisk has released a white paper for a synthetic performance of SSDs in 'virtual rpm' that quantifies the amount of revolutions a standard HDD would have to rotate to offer a similar performance. Sandisk cited 40,000vrpm for its SSDs, which is approximately seven times faster than a standard notebook hard drive.
Power play
SSDs are slowly making their way into high-end notebooks. A typical 80GB Intel X25-M Mainstream (MLC) drive goes for around RM2,000 from online retailers while Transcend sells a 64GB 2.5-inch MLC SSD at RM499 and is already available at local retailers. By simply replacing your existing HDD with an SSD, you get a faster boot time, longer battery life, greater reliability and a slight reduction in weight.
This story was first published in The New Straits Times.
