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| Solid State Drive |
The slowest component in modern computers relative to all others is the storage device -- and for most of us that's the hard disk drive (HDD). In this article we discuss why upgrading to a Solid State Drive (SSD) is a beneficial and sensible upgrade for almost any personal computer.
We'll be using two storage drives for testing and reference throughout the article:
HDD: Western Digital Scorpio Blue -- 500GB 5400RPM (WD5000BEVT)
SSD: Intel 320 series -- 120GB (SSDSA2CW120G3)
These models are considered midrange in their respective market segments; the WD Scorpio Blue is commonly included with new notebooks and the Intel 320 series is a popular aftermarket upgrade option.
The Fundamental Differences
The primary difference between SSDs and HDDs is moving parts; SSDs have none. An HDD is a mechanical device with spinning platters and read/write heads moving over them, sort of like a record player. The heads must move over the appropriate area of the platter while they're spinning to access data. The platters might have to spin around a few times in order for the read/write heads to access all the data.
An SSD on the other hand is one big piece of flash i.e. solid state memory. Data access is instant -- no waiting for platters to spin around.
SSD vs. HDD Performance Differences
There's a hard drive activity light on most computers -- it blinks whenever the storage drive is being utilized (reading or writing data). Whenever that light blinks the computer is waiting for the storage drive to finish its operations -- in other words, the storage drive is the bottleneck holding up the rest of the computer. This is especially the case when the computer is booting up, shutting down or launching programs. It's an even bigger deal with more than one program is requesting disk access, such as trying to copy files and do something else at the same time. Storage drives just aren't good at multitasking unlike processors.
We're using two benchmarks to gauge performance differences between SSDs and HDDs. The first is CrystalDiskMark (shown below) which measures minimum and maximum data transfer rates. Can you guess which is which without reading the captions?
There's more to this than just saying one is faster than the other, though. The top "Seq" bar, short for Sequential, symbolizes writing one big piece of data; this represents the drive's absolute maximum performance and is relative to copying files; the SSD is much better at it and better yet the performance is constant; hard drive performance can vary depending on whether data is being written on the inside or outside of the disk platters (the rotational speed is different).
The other three parts of the benchmark all refer to writing smaller pieces of data -- blocks from 4k to 512k (that's 1/256 to 1/2 the size of a MB, respectively; a typical MP3 song is 4-5MB). The computer spends most of its time accessing and writing these small blocks of data. The SSD shows its biggest relative gains here; the HDD isn't even in the same league.
Next we'll look at a more comprehensive benchmark involving simulated real-world usage; for that we turn to Futuremark's PCMark 7 storage subsystem benchmarks. Our test machine is an HP EliteBook 8740w running Windows 7 Professional 32-bit.
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| Western Digital Scorpio Blue -- 500GB 5400RPM (WD5000BEVT) |
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| Intel 320 series -- 120GB (SSDSA2CW120G3) |
I thought it would be useful to show not how much faster the SSD is but how fast the HDD is relative to the SSD; the final score shows it's only 29.5% as fast overall with a low of 5.1%. The lowest number comes from the "starting applications" part of the benchmark which is revealing; this involves a lot of reading and writing small files. Imagine opening iTunes; if it takes 30 seconds to open it with a hard drive, it takes less than two seconds with the SSD (theoretically).
Noise and Vibration
Hard drives require the presence of a motor to spin the platters inside; both the motor and the spinning platters create noise and vibration. It's minimal in most cases and the amount felt by the user depends on how it's mounted in the chassis. SSDs on the other hand just require electricity to power their processors -- there's no vibration and essentially no noise.
A side benefit of SSDs is that they aren't sensitive to vibrations and shock due to lack of moving parts; modern HDDs have various safeguards built in to prevent damage in case of shock and vibration but nonetheless are still more vulnerable to damage from such events compared to SSDs.
Types of SSDs
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| An example of a mSATA solid state drive |
The Intel 320 series in our test notebook is a traditional SSD -- it's the same size and shape as a 2.5-inch hard drive that is standard across notebooks. Another form factor has surfaced in the past year called "mSATA" (also called mini SATA). mSATA SSDs look nothing at all like a traditional storage device; they are more similar to memory (RAM) chips used in notebooks. They fit in PCI-e slots on a notebook's motherboard -- essentially the same connection that notebook wireless cards use.
The mSATA specification was developed so ultra-thin notebooks and devices like netbooks and tablets too small to house a standard 2.5-inch drive could have a standardized storage solution. It has the additional benefit of allowing normal-sized notebooks to take on an additional storage device without needing a second drive bay. Some notebooks are being sold with a standard hard drive and an "SSD cache" which means there's a small mSATA SSD inside slaved to the main storage drive. The SSD cache stores the operating system which has the benefits shown in the performance section above -- faster start-up and access times.
SSD Controller Options
What's a controller and why is it important? The controller is the input/output engine that handles read and write requests. For example when you open a document, the operating system submits a request to the storage drive and it's up to the controller to retrieve it.
Controllers are sold by several aftermarket vendors and SSD makers buy and customize them for their needs. Therefore even if SSDs from competing companies use the same model controller, it may be programmed differently and therefore will have different performance.
The controller market is extremely volatile; SSD makers may use two or even three different kinds of controllers in their SSD offerings. Marvell, SandForce, Link A Media (LAMD) and Indilinx are four controllers. Some SSDs are optimized to perform better in certain kinds of applications; it's really all up to how the controller is programmed.
Providing guidance on which controller is better is time-sensitive due to the market volatility. In the less-than five years SSDs have been around, we've seen controller companies go under, others turn their performance around to top the charts and new ones come up.
Your best bet for deciding on which SSD to purchase is to find the models that fit your price range and compare performance. Look at the whole package e.g. don't just pay attention to the controller; keep in mind the type of memory used in the SSD makes a difference in performance in addition to how the controller is programmed.
SSD Disadvantages
Why doesn't everyone have an SSD? The first reason is that they're expensive; hard drive storage might be as cheap as 15-20 cents/GB but SSDs hover near the $1/GB range. SSDs are much cheaper today than they were a few years ago (several dollars per GB); nonetheless the difference is still there.
Another disadvantage with SSDs is the limited storage capacity compared to HDDs; for notebook applications (2.5-inch drives) they're commonly found with only 256GB or so; larger drives exist but are exponentially more expensive and at some point it just isn't cost effective to spend that kind of money on a storage upgrade. Hard drives are readily available up to 1TB (1,024GB) in a 2.5-inch form factor.
Conclusion
An SSD upgrade makes sense for almost any personal computer owner looking for a boost in performance. We demonstrated in this article via benchmarks that SSDs can be up to 20x as fast as normal hard drives in various usage scenarios. SSDs have the additional advantage of producing no noise and vibration since they lack moving parts unlike hard drives; an added benefit of this fact is that SSDs aren't sensitive to shock and vibration. Using an SSD in a notebook improves its reliability.
Buying an SSD involves research -- the market is new compared to hard drives and changes rapidly -- companies, storage sizes, controllers and pricing. If you're not a PC expert you'll be happy to know that some SSDs are even available in "upgrade kits" that come with cloaning software that allows you to copy your old hard drive to the new SSD without needing to reinstall Windows or your applications.
Keep in mind that much of the SSD's performance depends on its controller; pay specific attention to that when looking at benchmarks. Some controllers are superior to others depending on the application (e.g. opening large files, launching programs and so on).
