Advanced format

Question

I read this in a superuser.com question:

The problem is that "Advanced Format" drives that simulate a 512-byte sector to the operating system but actually work with 4-kilobyte sectors internally is that a sector can only be written "in one go". In order to write to that second 512 byte area the entire 4KB sector must be read, and then re-written back to the drive, and this is a slower process than simply telling the drive to rewrite the whole 4KB sector.

Why can a sector be only written "in one go" in "advanced format"?

Answer 1

The on disk format is based around 4k sectors. That means 4k of data and a checksum over these 4k. If you could change part of those 4k then the data would be broken.

And that assumes that you can start writing with enough precision. Which is not the case and which is why we have gaps of unused space between sectors.

Answer 2

The sector being the minimum size which any hard drive will write at the hardware level. In the advanced format 4k drives it writes in the 4K. It can write many in a row, and it can write a 4k sector partly filled, but it is the chunk size which the disk operates. Not to be confused with the cluster size.