Much has been written about overprovisioning and its implementation on SSDs. In short, overprovisioning, or OP, is a portion of storage space on an SSD that is reserved for use only by the SSD controller. The three most common uses for this space are wear leveling, the replacement of bad blocks, and read-modify-writes. Overprovisioning serves to help increase both the longevity and performance of SSDs and it is a very common practice among SSD manufacturers.
However, some users would like to be able to buy their SSDs without the built in overprovisioning and make the decision to OP, or not to OP for themselves. They prefer the flexibility of deciding for themselves when to OP and how much space to use based on their specific needs. Corsair has announced and is now offering SSDs without this overprovisioned space.
Corsair SSDs with overprovisioning space typically have used 7% of the total SSD storage capacity. This means that users now have a choice with these new drives to use them with or without overprovisioning. Users can manually overprovision the drives if they wish or, they can leave them at their full capacity with no overprovisioning and enjoy the extra space.
For users of 256GB SSDs, this means they can have an extra 16GB of storage capacity on their drive over the equivalent 240GB overprovisioned SSD. Of course, RAID users will benefit even more as the number of drives is increased.
In reading some of that aforementioned information about overprovisioning, I've found a great deal of very useful information over at Anandtech. Here's a diagram from one of Anand's SSD articles highlighting how overprovisioning works.
To OP, or not to OP. That is the question. Whether tis nobler to the PC performance...