My SSD which was manufactored this year has a sector size of 512 bytes. Can it be changed to 2k or 4k while keeping the data. Using Windows 7. I want to benchmark and see if bigger sector size increased read/write speed.
While not truly sectors - because SSDs are not circular - the memory cells of an SSD are grouped into pages of 4 kB each. Pages are in turn collected in blocks of 512 kB (still not 512 bytes though).
Remember that SSDs cannot write to non-empty memory, but must clear entire pages of memory at a time, temporarily moving data to another location and back after the page has been cleared. This is why the TRIM command and garbage collection are important to keep an SSD in good shape.
I would guess that increasing the page size would increase the write overhead when the drive runs out of empty pages. Also, there really shouldn't be any benefit to reading more data at once, because of the low access times involved, as opposed to a rotating harddrive where you want to read as much as possible while the head is in the right place.
The 512B sector size reported by the SSD is only for compatibility purposes. Internally data is stored on 8kiB+ NAND pages. The SSD controller keeps track of the mapping from 512B to pages internally in the FTL (Flash Translation Layer).
I know that at least the SandForce SF-2600 controller supports various sector sizes, but to change the sector size requires a change in the firmware, which only the manufacturer can do. This is not something you can change after the fact, even if you were to have an SSD that supports other sector sizes.