>> In brief, every time an SSD updates a single byte anywhere on disk, it needs to erase and re-write that entire page.
> Is that actually true for SSDs? For raw flash it’s not, provided you are overwriting “empty” all-ones values or otherwise only changing 1s to 0s.
Maybe it depends. I wrote the driver for more than one popular flash chips (don't remember which ones now, but that employer had a policy of never using components that were not mainstream and available from multiple suppliers) and all the chips I dealt with did read and write exclusively via fixed-size pages.
Since SSDs are collection of chips, I'd expect each chip on the SSD to only support fixed-size paged IO.
> Is that actually true for SSDs? For raw flash it’s not, provided you are overwriting “empty” all-ones values or otherwise only changing 1s to 0s.
Maybe it depends. I wrote the driver for more than one popular flash chips (don't remember which ones now, but that employer had a policy of never using components that were not mainstream and available from multiple suppliers) and all the chips I dealt with did read and write exclusively via fixed-size pages.
Since SSDs are collection of chips, I'd expect each chip on the SSD to only support fixed-size paged IO.