On 2018-Aug-02, Thomas Munro wrote:
> PostgreSQL only requires atomic writes of 512 bytes (see
> PG_CONTROL_MAX_SAFE_SIZE), the traditional sector size for disks made
> approximately 1980-2010, though as far as I know spinning disks made
> this decade use 4KB sectors, and for SSDs there is more variation. I
> suppose the theory for torn SLRU page safety today is that the
> existing SLRU users all have fully independent values that don't cross
> sector boundaries, so torn writes can't corrupt them.
Hmm, I wonder if this is true for multixact/members. I think it's not
true for either 4kB sectors nor for 512 byte sectors.
--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services