self-encrypted disk and disk write prcess

Technical talk from Seagate

I will document the self-encrypted disk later. Almost all complexity likes in the bootstrapping process.

But here is the data write process within a seagate disk:

1. user data comes from the SATA interface, along with command, ecc code and dff code (to verify that data hasn't been modified)

2. Disk check the ecc code, the dff code, and recompute another checksum code (they have a name for it, I forgot). This chcksum code is being used afterwards, not the ecc and the dff code.
    If the data needs encryption, encryption is also done here.
    Note that this process happens *on the wire*. Only after the whole computation is the data going to be stored in the buffer cache

3. After data is in buffer memory, disk will do further processing:
   a. scagger (or another name?)  --- to filter out representative pattern in the dta
   b. ??? ---- to filter out repetitive bit string in the data?