Solid-State Drive(SSD)

     A solid-state drive (SSD) (also known as a solid-state disk though it contains no actual disk, nor a drive motor to spin a disk) is a solid-state storage device that uses integrated circuit assemblies as memory to store data persistently. SSD technology primarily uses electronic interfaces compatible with traditional block input/output (I/O) hard disk drives, which permit simple replacements in common applications. Additionally, new I/O interfaces, like SATA Express, have been designed to address specific requirements of the SSD technology.

     SSDs have no moving (mechanical) components. This distinguishes them from traditional electromechanical magnetic disks such as hard disk drives (HDDs) or floppy disks, which contain spinning disks and movable read/write heads.Compared with electromechanical disks, SSDs are typically more resistant to physical shock, run silently, have lower access time, and less latency. However, while the price of SSDs has continued to decline over time,consumer-grade SSDs are still roughly six to seven times more expensive per unit of storage than consumer-grade HDDs.

The proper care and feeding of SSD storage

Your solid-state drive sits there in silence. It’s sleek. Elegant. More than a little mysterious. The hard drive it replaced was easy to understand: A soft hum assured you that its platters were spinning. A quiet mechanical click informed you of its read/write operations. You’d groom it with the occasional defrag. Times were good.

Now? Everything seems peaceful. But you keep hearing stories: An SSD’s performance deteriorates over time. They have disturbingly short life spans. If it fails, your precious data will be consigned to oblivion. Facts? Or fever-brained fiction?

A high-end SSD is the pinnacle of computer storage today. Ditching your hard drive for one of the latest SSD models is like dumping your go-kart and hopping into a Formula One car. I’m not exaggerating: SSDs can produce a four- or fivefold jump in speed. They have no mechanical parts to break, and they emit zero noise. SSDs are the perfect storage medium—until things go pear-shaped. Or until you seek hard information about the technologies involved.

A speedy drive with a few deep secrets

One reason you hear so much fuzzy information about SSDs is that the companies that design and build one of the key components—the memory controller—guard their technology secrets more carefully than Coca-Cola protects its soda formula. It's a very competitive and lucrative market, with just a few players.

There are many more SSD manufacturers than SSD-controller manufacturers.

And some of the facts that are available sound scary. Consider the read/write longevity of SLC (Single-Level Cell) and consumer-grade MLC (Multi-Level Cell) NAND memory, the storage media used to build SSDs: The former is typically rated to last 100,000 cycles, but the latter is rated for only 10,000. Relax—you’d need to write the entire capacity of the drive every day for 25 years or so to wear out all the cells. The latest TLC (Triple-Level Cell) NAND that Samsung is shipping is rated for only a few thousand writes, but you’d still need to write the entire drive’s capacity for something less than ten years to use up the drive. No average user will ever come remotely close to that.

Life-prolonging techniques

Having the controller write to every NAND cell once before it writes to any cell a second time—a technology known as wear leveling—also helps to extend a drive’s life span. Wear leveling ensures that no cell endures heavy use while another sits virgin next to it. Newer controllers also compress data on the fly before writing it to the disk. Less data equals less wear.

The final longevity booster is spare capacity, or over-provisioning. All NAND chips have more memory than their stated capacity—about 4 percent. This is used by the controller for operations, and to take the place of worn out and defective cells. If you've ever wondered why some SSDs come in rounded sizes such as 120GB and 240GB, when other SSDs and memory in general is sold in capacities that are powers of two (128-, 256-, 512GB, etc.), it's because many vendors set aside even more NAND to extend the drive's useful lifespan. For example, a 240GB drive is really a 256GB drive with 16GB set aside for over-provisioning.

Higher capacity can mean better performance

With hard drives, the faster the spindle speed, the faster the drive. The amount of cache also comes into play, but by and large, a 10,000-rpm drive is faster than a 7200-rpm drive, which is in turn faster than 5400-rpm and 4800-rpm drives. That’s an easy and intuitive metric for comparison shopping.

There is no spindle in an SSD, but there is a comparative metric directly related to capacity. Up to around the 256GB level, PCWorld's testing has shown that a larger drive will be faster than a smaller drive, with other factors (such as the controller and the type of NAND) being equal. To understand why, you need to understand how data is written to SSDs.

Mechanical hard drives have moving parts that can destroy your data if they fail.

With a hard drive, data is basically written serially, down a single channel. The stream may be interrupted by existing data, but ideally it's all written in a neat, uninterrupted line. Inside an SSD, data is written in a scattershot, parallel fashion down multiple channels to the multiple NAND chips at once. The more NAND chips an SSD has, the more channels it has to write/read across, and the faster the drive will be.

You can find a perfect example in Intel's latest 525 mSATA (Mini-SATA) drives. Read the specs, and you'll see that the 30GB model is rated for 7000 4k operations (read-write operations) per second and 200 MBps sustained reading, while the 240GB version is rated at 46,000 4k operations and 550 MBps, even though both drives use the same 25nm NAND and identical SandForce controllers.

SSD optimization is unnecessary

Until recently, the common SATA 3-gbps interface was fine for any type of storage. A modern SATA 6-gbps SSD is backward-compatible with that standard, but it requires a SATA 6-gbps interface to realize its full performance potential. Soon enough, even that standard won’t be fast enough, as the fastest SSDs we've tested can already write at speeds nearing 5 gbps.

This is an Intel Series 525 mSATA (Mini-SATA) SSD.

Common wisdom indicates that there's really no way to optimize an SSD using a software utility. When you think of the manner in which data is written—scattered all over the drive—and the lack of a read/write head that you must worry about positioning, it's clear that the optimization techniques developed for mechanical hard drives don't apply to SSDs. In fact, the way an SSD presents data to your computer’s operating system bears zero resemblance to how it's stored on the drive. Wasting precious write cycles trying to optimize an SSD is counterproductive.

How TRIM prevents performance degradation

There was a time when an SSD’s performance would slowly degrade. That’s because writing data to a previously used NAND cell is a two-step process: The cell must be erased before it can be rewritten. To increase write performance, an SSD controller would simply mark a used cell as no longer active and write data only to cells that had never been used. Once all the cells were used a single time, the drive’s write performance would deteriorate because its controller had to erase cells before it could write to them again.

Nowadays, we have the TRIM command (it’s not an acronym, despite the capital letters). TRIM is an operating-system order that instructs the SSD’s controller to preemptively erase used cells containing unneeded data. TRIM is supported in Windows 7 and later, and it ensures that your SSD's performance will remain at its peak over time.

Recovering data from a failed SSD

SSDs, and solid-state storage in general, have a disturbing tendency toward binary functionality. An SSD failure typically goes like this: One minute it's working, the next second it's bricked. The latest drives are supposed to alert you when they’re nearing the end of their useful life span, but what happens if the warning pops up and you’re not there to see it? The solution, of course, is to back up your SSD in advance.

Contrary to common belief, however, data can be recovered from a failed SSD. DriveSavers, a California firm known for recovering data from hard drives that have experienced the most catastrophic failures, can perform the same service on SSDs. Whether the failure lies with the controller or the NAND itself, the company has a good, though not perfect, success rate.

That 'dead' drive may just be awaiting rescue

How is this possible? Many times, what seems like a hardware failure is actually a firmware failure. The controller simply encounters a situation it can't deal with, and locks up. If the controller is bad, you can replace it—provided that you can find the exact, correct model. Remember when I said that only a few companies are building memory controllers for SSDs? Well, some SSD manufacturers use what might look like an off-the-shelf controller when it’s actually one built to their own specifications.

De-soldering chips is a painstaking task. I know—I’ve done it myself. DriveSavers has a robot for that work, or it would never be able to operate cost-effectively. The company has also developed proprietary recovery software that can re-create data from just the NAND itself, even if a bad chip is involved. Company reps were understandably vague when I asked about DriveSavers’ techniques, but the bottom line is that you might be able to recover data from a failed SSD.

Some final SSD tips

SSDs are wonderful storage devices, but they're not perfect and they're not all equal. A no-name bargain unit might not be as good of a deal as you think because it probably uses slow NAND and an outdated controller. Shop carefully. Here are some additional tips:

• Buy the highest capacity you can afford. You’ll get better performance, although the benefit declines rapidly beyond 256GB.
• If you’re running an OS that doesn’t have native TRIM support, check the manufacturer’s website for a driver that will force garbage collection. You might also look for a utility that you can run occasionally to perform the same task.
• Use your SSD for the computer’s operating system and application software. Store your movies and most of your other data on a mechanical hard drive. Hard drives stream media just fine, and they’re often better suited for simultaneous recording and playback. They're also at least ten times cheaper per gigabyte.

SSDs may seem exotic and mysterious, and they're still pretty expensive. But they have significant performance advantages over traditional mechanical hard drives. Now that you know their secrets, you can shop smarter for these sleek storage devices and take the best care of the one you bring home.

How to stretch the life of your SSD storage

Once a PC enthusiast's dream storage device, the solid-state drive (SSD) is quickly becoming commonplace in custom PC builds and retail desktops alike. After taking a detailed look at SSD technology, we're moving on to basic care and feeding—how to stretch the life of your drive. All it takes is a little education, and some new ways of managing storage that have nothing to do with your traditional hard drive's maintenance routine.

What wears down an SSD?

An SSD is flash storage. It has no moving parts. So unlike on a traditional mechanical hard drive, nothing breaks. SSD wear and tear has to do with write cycles.

No moving parts in NAND flash drives.

Flash storage handles data in a specific way. When data is written to a block, the entire block must be erased before it can be written to again. The lifespan of an SSD is measured in these program-erase (P/E) cycles. Modern, consumer-grade, Multi-Level Cell (MLC) NAND memory can generally endure about 3,000 to 5,000 P/E cycles before the storage's integrity starts to deteriorate. The higher-end, Single-Level Cell (SLC) flash memory chip can withstand up to 100,000 P/E cycles.

You'd have to work hard to reach the P/E cycle limit for an MLC-based drive, let alone an SLC-based one. Nevertheless, every time you write something to the drive, you bring it a little closer to its demise. Don't obsess over every single write cycle—a few of our later tips are best suited for such tendencies—but do check out the following techniques for minimizing unnecessary writes to the drive.

No more defragging

First and foremost, your days of worrying about fragmented files are over. Because there is no moving read-write head, and because of the nature of flash memory and controllers, fragmentation as you understand it does not exist with SSDs. In fact, defragging makes numerous small, unnecessary, device-killing writes to the SSD—reason enough to eliminate it from your routine.

You should defrag only your non-SSD drives.

To turn off your disk defragmenter, uncheck the Run on a schedule box in the defragmenter program. If you have hard disks that would benefit from a good defragging, you can run the defragmenter on a schedule for those particular disks.

Disable search indexing

The search indexer made searching for files on a traditional hard drive speedier, but it doesn't do much on an SSD except perform small writes. That's a no-no! Disable it by searching for "services.msc" in the Start Menu search box

Disable Windows Indexing

Find and right-click Windows Search to open the properties. Stop the service and set the 'Startup type' drop-down menu to Disabled.

What to put on SSD, what to put on HDD

Another key to SSD longevity is to use it for the right kind of data. SSD is great for applications, operating systems, and games, to crush load times and boot up applications at lightning speeds. There'd be nothing wrong with using SSD for data such as music, pictures, movies, and documents, but you don't need the speed—and you probably wouldn't want to waste write cycles on constant uploads and edits. A traditional, mechanical hard drive would suffice for the latter kinds of files.

Hibernating uses more writes

For those who have an SSD-endowed laptop, note how hibernation mode differs from sleep mode in SSD usage. When your computer hibernates, it stores open documents and programs to the SSD and shuts down completely. Sleep will pause everything, but it won't write to the drive.

There are downsides to sleep mode: It uses a little more energy than hibernation, and if your battery runs down, those sleeping files are toast. In the case of an SSD, however, it makes economic sense in the long run to use a little extra power to avoid making unnecessary writes to the drive every time you step away from your system.

To disable hibernation, simply open your command prompt, type powercfg.exe /hibernate off (without any end punctuation), and press Enter. No more hibernating!

Bonus tip: optimizing performance with TRIM

The TRIM command solves a performance problem that eventually crops up in SSDs over the course of continued use. As noted above, when a block is written to, the entire block must be erased before it can be used to store new data. But the erasure process can slow the drive's write performance if managed on the fly. The TRIM command steps in a little ahead of time and instructs the operating system (supported by Windows 7 onward) to erase data blocks that are no longer in use, preparing them to be written to directly without further ado.

A "0" means TRIM is enabled.

Windows 7 and 8 should detect an SSD and enable TRIM automatically if the drive supports it—but it's a good idea to check anyway. Open the command prompt and typefsutil behavior query disabledeletenotify (without any end punctuation). If you get 'DisableDeleteNotify = 0' as a response, you're set. If you don't, confirm that your SSD drivers are up-to-date.

So just how long will it last?

While these techniques should wring more life out of your SSD, the truth is that vendors are loath to discuss drive longevity in greater detail. We happened upon an industrious German computer programmer who crunched some numbers and came up with this chart:

EF.GY

The chart shows the wear on different-size drives after continuous writing at 6 gigabytes per second (GBps) to get to approximately 100,000 P/E cycles. This test would never happen in a natural setting—there's no way to continuously write 6 GBps with today's tech—and it's far more punishing than anything a regular user would do. The smallest drive lasted for nearly 2 months, while the largest lasted for more than a year. Quite the troopers.

For the average user who doesn't write heaps of data to storage constantly, your SSD will probably live a long and happy life. And if you adjust your storage habits to the SSD's strengths, you could squeeze a few more cycles out of the drive.