Friday, March 13, 2009

SSD: The Spin Stops Here…

So who out there has ever experienced a Hard Disk failure? Sure, a lot of you have. Current magnetic spinning disks are (very) slowly being replaced by faster, longer lasting, Solid State Disks. Solid State Disks are nothing new. But they do offer many benefits over their predecessor. The major benefits over older technology are what really set apart this new technology.

With no moving parts, higher resistance to dropping and lower power consumption, laptop users are loving this new technology. Accident prone people who drop their laptops are enjoying their data staying put, road warriors are enjoying longer battery life, and power users are enjoying longer disk life.

The market share for Solid State Disks is relatively small at this point in time. Some people project the whole solid state market to be at 7.5 Billion in 2012, whereas the current market for Seagate (a hard disk manufacturer) was 3 Billion… just for the third quarter of 2008. So the traditional hard disks aren’t going anywhere soon.

So when a drive fails, how easy is it to retrieve the data from the drive? Depending on the drive size and whether or not there is any type of drive encryption, it is fairly easy given the proper tools. This trend is about to change with SSDs. SSDs don’t use the same technology that the traditional SATA (Serial Advanced Technology Attachment) and PATA (Parallel Advanced Technology Attachment) drives do.

But what kinds of issues are still alive for SSDs? Well, the costs are still outrageous for the common end user (especially in today’s economy). Disks are small in size, averaging 64GB of space for $150 which puts them on par with current SAS (Serial Attached SCSI (pronounced Skuzzy)) Drives. SAS Drives are built for Servers and offer stunning specs, including lots of cache, 10,000 and 15,000 RPM spin speeds, and lightning fast response times. Older desktop and laptop drives spin anywhere from 4600RPM to 7200 RPM which makes them much slower, but at the same time more affordable.

SSDs also are able to endure more abuse. This is rated in G-force. One G is equal to a mass’ normal weight. SSDs are able to take 1500G and more; that is 1500 times its own weight! This happens when a hard drive is dropped. Traditional drives can’t take that much abuse, while SSDs are said to be able to be dropped off of a 2 story building and still work. Try that with a normal SATA drive.

Think of your USB thumb drive that is used to transfer files from computer to computer; that is the type of technology used with Solid State drives. The difference is that traditional HDDs seek data at specific memory locations that are assigned distinct locations on a platter of the hard disk. SSDs don’t have this because there isn’t a spinning platter. This is what is called NAND Technology. This technology makes these drives much faster than traditional HDDs. You can’t physically point out a location for memory in NAND technology.

There are two types of Flash Memory; NAND and NOR. While NOR is best suited for small memory sticks, NAND is used in USB and now SSDs. NOR operates by sending electrical signals to the cells that form the whole storage memory. Each cell contains either a 1 or a 0 and all of those 1s and 0s make up your files, pictures and word documents. NAND on the other hand, operates by using gates. Writing data is called “tunnel inject” and reading data is called “tunnel release.” Because of how data is stored in flash memory, access times are significantly faster. Flash memory just about instantly accesses the data location and responds. In some cases random access times are dropped to 1-3ms! Traditional hard disks have normal access times of 7-10ms.

Also, these data locations are stored in onboard RAM that can have almost instant access to a memory location allowing for up to 250MB/sec data access. To put that into perspective SATA drives work at about 40-70MB/sec and PATA drives are even slower. So moving large files, such as MP3s and AVIs, goes much quicker (on the order 4-7 times faster!) This is most significant when moving Gigabytes of data.

Comparing three types of drives, SATA, SAS and SSD, how do you know what to do these days? There are many factors that can affect your decision. Cost, speed, reliability, MTBF (Mean Time Before Failure), form factor and transfer speed. Well for now, in mobile platforms, you will most likely be looking at SATA drives, although, if you have the extra money you could get a SSD. The server market eventually will be using SSDs but for now they are still using older SCSI drives or newer SAS drives. Normal desktop machines will probably be the last to move to SSDs due to size. People with 500 GB of music and terabytes of movies won’t be able to afford SSDs to replace their SATA drives for at least another 5-10 years.

The biggest issue with hard drives is that hardly anyone backs up their data. Even today, with disk space so cheap, backups are still almost non-existent in the home. Businesses are doing much better these days than even a few years ago in backing up data, but these backups are still on slow tapes that still take a lot of time to backup to and restore from.

So what’s the moral of the story? SSDs are moving in at a slow pace. But eventually all hard drives will be some kind of non-mechanical disk. They are energy efficient, fast and very long lasting. Even so, if the MTBF is 1,000,000 or longer as advertised by many SSDs, backup is crucial to data. Multiple copies of data in multiple locations is the only safe way to store data. What happens when a disk fails? That’s when you call us to get your data back.

3 comments:

Matt Davis said...

Do you think that SSD represent any sort of challenges or advantages from a forensic standpoint? If a platter based drive dies, you can still send it out to get read. What about SSD? Are there differences in how data is spread out and what that would mean for capturing file fragments?

Alex Hamerstone said...

Are there any issues with heat? I would assume SSDs run cooler.

Steve Erdman said...

Matt, as far as Forensics Analysis goes, there are major issues that come into play. Specifically what part of the SSD fails. If the memory modules fail, you can basically kiss the drive goodbye. The way information is spread across the drive, it may reside on multiple memory modules. Even if it doesn't reside on multiple modules, you my lose the module your data was on. In either case, you are looking at MAJOR cost involved in hiring a company to solder new modules in place, which, as far as I can see, hasn't been done, and probably not even attempted. If a section of the board goes bad, the drive is basically fried. In any case, you should always look at backing up your drive! :)

And Alex, you bring up a good point. Not only do SSDs run cooler than older SATA/PATA/SAS/SCSI drives, they also run on far less power constraints. This helps bring the TWP down in laptops which in turn helps drastically extend battery life.