On 15/01/2023 12:13, Reindl Harald wrote:

Am 15.01.23 um 13:00 schrieb Pascal Hambourg:

quoted

Linux RAID supports TRIM/discard, but what does it do exactly ?
Does it only pass-through TRIM/discard information to the underlying 
devices or can it also store information about which blocks contain 
valid data in the superblock metadata?

pass-through TRIM/discard

it makes no sense to store that on the RAID layer - if someone is th 
eposition to store the information to reduce the fstrim load after a 
reboot it's the filesystem on-top

It makes EVERY sense to store it in the raid layer when you're doing a 
rebuild.

I would like to store it there for that exact reason - if you've lost a 
drive and are in a recovery situation, then you can ignore parts of the 
drive that don't contain filesystem data, because TRIM has told you they 
don't.

afaik, however, nobody has got round to coding that, because it's a lot 
of work and probably not financially worth doing. If someone wants to do 
it for the love of it, great!

Cheers,
Wol