On Mon, 17 Oct 2016 11:31:48 +0100, John Rumm
wrote:

On 17/10/2016 10:45, The Natural Philosopher wrote:
On 17/10/16 09:37, John Rumm wrote:
In reality it could be anywhere on any boundary the
SSD firmware and processor puts it.

Not quite - there is not a one to one mapping of OS allocation units to
flash pages. For optimum performance you need to ensure that whichever
allocation unit you update, the SSD can do that update by operating on
one (and only one) page of flash. With the wrong alignment, you can end
up with the SSD needing to do two page updates for each OS allocation
unit update.


However all that may be true, but its not under user level control via
partioning, and its handled internally by the SSD.

There is no obvious way a SSD could make a sensible choice to internally
remap alignment if it turns out you have managed to install an OS
partition with a start LBA offset from the ideal. Especially as one
physical drive can host more than one partition, and if you really
tried, you could end up with several partitions each with different
alignments.

It makes far more sense to ensure the partitions are aligned so that the
OS allocation unit is on a 4K boundary (which is the default action on a
modern OS anyway)

So and irrespective of any performance impact ITRW, if some software
(Gparted) can see and display that these alignments aren't made *and*
can set them, is Gparted actually then *actually / physically*
resetting said alignments or just indicating it is?

What would be a good (valid) way of checking for such things
(increased performance hopefully) pre and post adjustment?

It all sounds like re-numbering sector to reduce latency with Optune
all those years ago. ;-)

Cheers, T i m