When I try to use TrueCrypt or VeraCrypt, write speeds are very slow, but read speeds are fast. This happens with both programs, and it occurs regardless of whether I'm using an encrypted file container or an encrypted partition. (So, no, this isn't fragmentation etc.)
For example, on my SSD where unencrypted read and write speed both benchmark over 1GB/s on CrystalDiskMark, an encrypted volume using AES-XTS and HMAC-RIPEMD-160 benchmarks read speeds of 810 MB/s vs. write speeds of 40 MB/s.
Why are encrypted writes so much slower than encrypted reads?
(And no, I'm not doing something silly like benchmarking in a VM. I swear I've already thought of all the "easy" answers and they don't explain the situation as far as I can tell.)