Solid-state drives ("SSDs") have been in the market for some time, first leveraged in consumer devices, and then laptops, notebooks, and desktops. SSDs are not new; in fact, they have a long 30 year history. As capacity, reliability, and performance have improved over the years, coupled with DRAM advancements and price declines, solid-state drives have now hit a cross over point, making them available and affordable for enterprise-class server and storage solutions. Let's explore this a bit.
What is a solid-state drive? An SSD uses either flash non-volatile memory - NAND or NOR (NAND flash has faster write and erase times than NOR), or DRAM volatile memory to emulate a traditional spindle / platter hard drive device ("HHD"). SSDs can directly replace HDDs.
Today's SSD capacities range from 32GB, 64GB, 80GB, 100GB and most recently, 160GB. In the HDD world, one measure of advancement was platter technology; replace "platters" with "planes" in the SSD world. As planes and channels are interleaved with front and back-end caches - all colliding within a 2.5 inch-wide space - capacities will rapidly increase to 200GB, 300GB, 400GB, and 500GB. It is my opinion that innovation dollars will rapidly transition from spindle technology to plane technology, and, as a result of that transition, the pace of SSD capacity expansion will galactically outpace HDD. Consider, in the late 1980's, there were 5.25 inch 110MB drives. Twenty years later, there are 2.5 inch 1TB drives (check out this great picture). It could take SSDs five years, not twenty, to make similar progress. For example, by 2011, we could see the first 1TB SSD.
What are the advantages of SSDs over HDDs? There are many and they are compelling.
First and foremost, there are no moving parts, and thus, no rotational vibration, which dramatically increases reliability.
Second, SSDs require very little power at idle (less than a watt) and maximum usage of 2 - 4 watts. In fact, the power profile is so compelling, suppliers are measuring work done using Joules (1 watt hour = 3600 J). Said differently, at idle, SSDs consume less than 108 Joules (0.3 Watts/hr).
Third, acoustically, SSDs are essentially silent. The Threshold of Hearing ("TOH") is 0 dB. A whisper is 20 dB. Normal conversation is 60 dB. SSDs operate between 0 and 2 dB.
Fourth, given that we are now in the world of solid state, you can run your data center at a higher temperature. I have always believed that data centers just need to turn up the thermostat, reducing the power consumption of Computer Room Air Conditioning (CRAC) units. SSDs are yet another reason to do so.
And finally, and I think the most compelling advantage: performance. SSDs will have faster read and write speeds with near zero access times. For example, when benchmarking Intel's X25-M SSD, random read IOPS is 9x that of 7200 RPM HDDs and 11x faster for random writes (both on 4k transfer sizes). Further, sequential read performance is over 200MB/s, and sequential writes are over 70MB/s. This is pretty impressive performance, whether it is random reads, random writes, sequential reads, or sequential writes.
In sum, SSDs are smaller, cooler, faster and more reliable and now highly applicable to enterprise workloads.
To be balanced, there are some potential drawbacks, and I remember them by using the 3 C's: Cost, Capacity and Cycles. First, there is the cost. SSDs are between 5x and 10x the cost per GB of HDDs. A year ago, the ratio was as high as 30x. Second, HDD technology is 10x the capacity of the largest capacity SSD. Third, there is a lifetime limit on the number of erase/program cycles per "cell." The component NAND cycle capability combined with an SSD's NAND management algorithms determines the life span, or endurance of the SSD. The quality of those NAND management algorithms varies from one SSD vendor to another. Having said all that, cost is declining, capacities increasing, and memory write algorithms improving. To mitigate the drawbacks, just keep in mind a few simple items when considering an SSD: know your application, know the usage model (reads and writes), and know what is important (sequential or random) to optimize performance.
Lets look at some real products from Intel. Intel is currently offering three SSD solutions: the X25-M, X18-M, and X25-E. The X25-M is targeted for mobile devices. I like the X25-M (up to 160GB MLC) for read intensive applications - fast boot drive, fast search and small but fast video bursts. The X18-M (1.8 inch form factor) is targeted at even smaller form factors. Finally, the X25-E targets enterprise solutions. The X25-E is a great SSD for write intensive, highly random workloads. It is a 2.5 inch form factor drive that delivers up to 64GB SLC (single-level cells) capacity and 240MB per second reads and 170MB per second writes. It also supports a 3.0GB/s SATA interface and has 2M hours MTBF. Intel has delivered a very impressive solution set as SSDs enter the data center. Rackable is pleased to support Intel's complete SSD line.
All things die and are replaced by another form. So it will be with HDD and SDD. We will see it first in laptops (the small and the weak go first). Next will be boot and read servers (the really fast), followed by the mainstream server (somewhere in the middle). The march to the solid-state server (no moving parts) is unstoppable.
This will indeed be a solid state of the union.