SSDs are a bit of a long discussion, but I'll cross-post and expand upon an answer I wrote in the Mac WDE forum.
We introduced AES-128 support, multi-processor support, and other performance enhancements (including AES-NI on Windows) to help SSD performance. We're working on other optimizations, but there are some fundamental challenges - for example, by default WDE encrypts an entire disk, even unused sectors. This improves security, since an attacker can't tell an empty drive from a full drive. However, this writes to every sector of an SSD and makes every future write a re-write - which are significantly slower on SSDs.
To combat this, we introduced a command line option: --fast. If you encrypt using this option, it doesn't encrypt blank sectors. Due to security considerations, this is an advanced option only available on the command line.
If two drives are encrypted with --fast, it's easy to tell which has more data (and therefore which to attack). A fundamental premise of encryption is to obscure the value of the content, so a blank document and a document full of text should be indistinguishable (see Wikipedia's entry on block cipher modes of operation for an interesting example of what happens when this goes awry). Using --fast leaks information that could be useful to an attacker, so (as security people), we don't like it.
I've heard very mixed reactions to this option from customers: generally, it sounds good at first, but then customers consider the above and decide not to use it. I'd be interested in your input on whether you would use this - also, what could we say to provide the "average" user with enough information to make an informed security vs. performance trade-off without it being too much detail?
Bryan Gillson
Sr. Director, Product Management
Encryption