Defrag Like It's 1993

Re:Defrag Like It's 1993 by 5e92cb50239222b on Friday December 17, 2021 @12:30AM (#29588212)

I always read (from sources like LKML, not random blog posts) that defrag on SSD is simply useless because you never know the actual physical placement of your blocks. You can write a sequential 512 MB chunk of data in a single file and have it exploded in 500k+ 4k blocks in different locations (or vice versa — a bunch of random writes to different sectors can be compacted into a single linear block).

If you really need to defrag SSD (which somewhat helps IME if it was heavily used up to 100% capacity), copy everything to other storage, wipe it (preferably with NVMe/SATA commands, or at least do a full TRIM), and then copy everything back.

[ Parent | on HN ]

Re:Defrag Like It's 1993 by hansel_der on Friday December 17, 2021 @09:44AM (#29592813)

if your first assertation is correct, and ssd's use internal mapping of physical and logical sectors, then your suggestion with wiping/rewriting would not work.

i know that per SMART, disks (hdd and ssd) have to have extra space that will be used if an active sector goes bad, but idk about the total internal remapping on ssd's.

[ Parent | on HN ]