The SSD Relapse: Understanding and Choosing the Best SSD

jmke · 31st August 2009, 12:26

The falling performance was actually a side effect of the way NAND flash works. You write in pages (4KB) but you can only erase in blocks (128 pages or 512KB); thus SSDs don't erase data when you delete it, only when they run out of space to write internally. When that time comes, you run into a nasty situation called the read-modify-write. Here, even to just write 4KB, the controller must read an entire block (512KB), update the single page, and write the entire block back out. Instead of writing 4KB, the controller has to actually write 512KB - a much slower operation.

http://anandtech.com/storage/showdoc.aspx?i=3631

jmke · 31st August 2009, 13:29

Quote:

Holycrapwtfbbq?

lol

31st August 2009, 12:26	#1
jmke Madshrimp Join Date: May 2002 Location: 7090/Belgium Posts: 79,021	The SSD Relapse: Understanding and Choosing the Best SSD The falling performance was actually a side effect of the way NAND flash works. You write in pages (4KB) but you can only erase in blocks (128 pages or 512KB); thus SSDs don't erase data when you delete it, only when they run out of space to write internally. When that time comes, you run into a nasty situation called the read-modify-write. Here, even to just write 4KB, the controller must read an entire block (512KB), update the single page, and write the entire block back out. Instead of writing 4KB, the controller has to actually write 512KB - a much slower operation. http://anandtech.com/storage/showdoc.aspx?i=3631 __________________