by Atelo » Sat Feb 06, 2010 4:20 pm
Antilikos wrote:Are these things some sort of genetically engineered fungus or something? I don't get the degradation thing...
As you probably know, your USB Flash Stick has limited writes. Usually around 10,000 writes before it can start to fail. For an operating system constantly writing to the hard drive, this isn't much at all.
To counter this in SSDs, the drive never writes to the same spot over and over. Instead it writes to the next unwritten section. Even if you open a document, add one word and save it, it is not written to the same spot. It goes to the next area that hasn't been written to. Once the entire drive is full, it starts over. This means every bit of flash memory gets used instead of one small section.
Flash memory needs to be erased before it can be written to. Once it starts over, it must erase the old information before it can write. This slows down writing significantly and kills performance. Normally when you delete a file with our current hard drive technology, the file isn't actually deleted. Only the reference to the file is deleted and it is still sitting on your drive, allowing you to "Undelete" so long as the information isn't overwritten. Because SSDs must erase data before writing it, all that deleted information slows it down when it comes around for another pass.
The TRIM command supported by Windows 7 tells the drive to actually delete the file instead of just deleting the reference to the file. This allows the performance of the drive to stay within acceptable limits for longer because when it comes around for another pass, the information is already blanked out.
Basically SSDs are brand new and our current file system and hard drive tech wasn't designed with their requirements in mind. It will only get better from here on.
[quote="Antilikos"]Are these things some sort of genetically engineered fungus or something? I don't get the degradation thing...[/quote]
As you probably know, your USB Flash Stick has limited writes. Usually around 10,000 writes before it can start to fail. For an operating system constantly writing to the hard drive, this isn't much at all.
To counter this in SSDs, the drive never writes to the same spot over and over. Instead it writes to the next unwritten section. Even if you open a document, add one word and save it, it is not written to the same spot. It goes to the next area that hasn't been written to. Once the entire drive is full, it starts over. This means every bit of flash memory gets used instead of one small section.
Flash memory needs to be erased before it can be written to. Once it starts over, it must erase the old information before it can write. This slows down writing significantly and kills performance. Normally when you delete a file with our current hard drive technology, the file isn't actually deleted. Only the reference to the file is deleted and it is still sitting on your drive, allowing you to "Undelete" so long as the information isn't overwritten. Because SSDs must erase data before writing it, all that deleted information slows it down when it comes around for another pass.
The TRIM command supported by Windows 7 tells the drive to actually delete the file instead of just deleting the reference to the file. This allows the performance of the drive to stay within acceptable limits for longer because when it comes around for another pass, the information is already blanked out.
Basically SSDs are brand new and our current file system and hard drive tech wasn't designed with their requirements in mind. It will only get better from here on.
