22Jan 09
Five reasons SSDs are great
Posted by Alex Serpo @ 15:55 27 comments
It's rare that we see a genuinely new technological paradigm land on retail shelves. Solid state drives, or SSDs, are one such technology, and have only just begun to limp onto the market at strictly enthusiast prices.
With close examination, it seems that the days of the good old mechanical hard drive are numbered, with SSDs ready to eclipse them in the long run. Here are five reasons to look forward to the ascendancy of SSDs.
1. Speed
First, some background. Unlike mechanical hard drives, SSDs don't contain any moving parts. Rather, they rely on millions of tiny flash memory cells. These tiny flash cells are non-volatile memory, meaning that they retain their data even when no power is present. Today SSDs most commonly utilise NAND-based flash memory.
This means no moving parts, and thus no spin-up speed, which results in shorter boot times. It also means faster read speeds from idle, and faster write speeds for larger files (unfortunately, due to the nature of their design, SSDs struggle with writing smaller block sizes, see here for more details).
Realistically, this results in hard drive access which is about 60 per cent faster — the score we achieved for a file transfer when comparing Intel's latest X-25M SSD with a 7,200rpm Seagate drive.
Or, for a more practical demonstration, here is a video featuring the MacBook Air.
2. Power saving
There is still a lot of debate around this, but it is safe to say that generally, SSDs have a lower power consumption than conventional hard drives (if only marginally so). This varies depending on the test, the SSD, and the mechanical hard drive you are comparing the SSD to.
However, what we can say is that in the long run, flash-based SSDs have one up on mechanical hard drives in the power consumption stakes. Comprehensive tests performed by Tom's Hardware show that while average power consumption is comparable between SSDs and mechanical hard drives, when optimised, SSDs can achieve a much lower average power requirement and performance per Watt figures.
3. Size
This one is a bit of a no-brainer, SSDs can be much smaller than mechanical hard drives. While they are generally packed in similar form factors to mechanical HDDs (1.8, 2.5 and 3.5 inches), they have the potential to be much smaller. MicroSD cards are a good demonstration of this, as is the seemingly endless increase in the capacity of USB keys. The ability to put a huge amount of storage into a tiny space creates new opportunities in gadget design — iPod Pico anyone?
4. Durability
It is said that the enemies of reliability are heat and moving parts. SSDs have no moving parts, meaning that they aren't susceptible to the vibration or drop damage associated with mechanical disk drives.
The nature of flash memory also means that it can survive through a larger temperate range, with some flash drives operating at up to 70 degrees Celsius.
It is safe to say that generally, SSDs have a lower power consumption that conventional hard drives
Write cycles vary markedly depending on the grade of SSD you are looking at. There are two kinds of flash memories available in SSDs: single level cells (rated at around 100,000 cycles), and multi-level cells (rated at round 10,000 cycles). This whitepaper provides more details.
Technologies such as wear levelling can increase durability, as can other improvements. Improvements can allow as many as 1 million write cycles, a value which allows for continuous use over decades. Given that mechanical hard drives are normally rated around 50,000 read/write cycles, SSDs currently have competitive durability and the potential to surpass mechanical hard drives.
5. The best is yet to come
This is the most important point of the five. SSDs are a fledgling technology, and currently aren't living up to their potential. Mechanical hard drive technology, on the other hand, is mature and so is seeing its limits pushed.
The first thing we can expect from SSDs is a dramatic fall in price. Secondly, we can expect steady increases in both storage capacity and reliability.
Finally, current software is optimised for use with mechanical disks, particularly more recent versions of Windows. As SSDs perform better under certain conditions (such as writing larger memory blocks), so software can be optimised to work with SSDs. This means software optimisation can parallel hardware optimisation, providing further headroom for improvement.
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The ioDrive by Fusion-io shows what can happen when flash bypasses SATA and is put on the PCIe, providing 700MB/s read and 600MB/s write.
But Flash has the potential to replace DRAM, leading to the scanario where installing programs effectivelly makes them in RAM and ready for immediate running.
Computer s could have TBs of direct CPU storage. Computer boxes would be completely redesigned as thare would be no HDDs requiring their own cages for vibration isolation and heat dissipation.
We are on the cusp of a real computing revolution.