On 16.02.2020 03:32, Arno Wagner wrote: > Hi David, > > using LUKS should not result in write-amplification. > LUKS uses 512B blocks and just provides an 1:1 mapping. Using defaults it does cause a higher write-amplification. By default dm-crypt doesn't not enable discard-support, whereas it is normaly supported for an unencrypted filesystem. And given that at least some distributions even install a fstrim-cronjob, the filesystems are trimmed, even if not mounted with the discard-option. This results in an unencrypted filesystem having it's empty space "empty", as far as the SSD is concerned. Wheras "empty" space (either "is" or "stays") "used" for a LUKS device. The "is" or "stays" difference comes with having the encrypted device pre-inited or not. With pre-init the blocks are always "in use". Without pre-init the blocks are "unused" as long as they aren't written and switch to "in use" after first beeing written, after which they will stay "in use" forever. Less "empty" space results in higher write-amplification because the SSD has to remap "empty" space as it is "in use", as far as the SSD is concerned. A pre-inited encrypted device, in this scenario, never has any empty space. I'm not saying that you can't make it equivalent, just that there are differences when using the defaults. > On Sun, Feb 16, 2020 at 01:59:41 CET, David Niklas wrote: > > Hello, > > Today I was helping a poor luser who's Crucial P1 QLC SSD died from > > too many writes. We still don't know what's doing the writing, but he is > > running luks using FDE so write amplification is definitely a > > factor. > > I forget the answer to this so please enlighten me, is there a streaming > > cypher he can use instead of a block cipher? A better option that I > > didn't consider? > > Not that the TCG Opal is to be fully trusted (nor is it available on > > that model), but how does it work with respect to write amplification vs. > > luks? > > > > Thanks, > > David > > _______________________________________________ > > dm-crypt mailing list > > dm-crypt@xxxxxxxx > > https://www.saout.de/mailman/listinfo/dm-crypt > > -- > Arno Wagner, Dr. sc. techn., Dipl. Inform., Email: arno@xxxxxxxxxxx > GnuPG: ID: CB5D9718 FP: 12D6 C03B 1B30 33BB 13CF B774 E35C 5FA1 CB5D 9718 > ---- > A good decision is based on knowledge and not on numbers. -- Plato > > If it's in the news, don't worry about it. The very definition of > "news" is "something that hardly ever happens." -- Bruce Schneier > _______________________________________________ > dm-crypt mailing list > dm-crypt@xxxxxxxx > https://www.saout.de/mailman/listinfo/dm-crypt -- Matthias _______________________________________________ dm-crypt mailing list dm-crypt@xxxxxxxx https://www.saout.de/mailman/listinfo/dm-crypt
