On Tue, 2025-03-18 at 23:59 +0000, Trond Myklebust wrote: > On Tue, 2025-03-18 at 16:52 -0700, Rick Macklem wrote: > > On Tue, Mar 18, 2025 at 4:40 PM Trond Myklebust > > <trondmy@xxxxxxxxxxxxxxx> wrote: > > > > > Yes, I also realise that none of the above operations actually > > > resulted > > > in blocks being physically filled with data, but all modern flash > > > based > > > drives tend to have a log structured FTL. So while overwriting > > > data > > > in > > > the HDD era meant that you would usually (unless you had a log > > > based > > > filesystem) overwrite the same physical space with data, today's > > > drives > > > are free to shift the rewritten block to any new physical > > > location > > > in > > > order to ensure even wear levelling of the SSD. > > Yea. The Wr_zero operation writes 0s to the logical block. Does > > that > > guarantee there is no "old block for the logical block" that still > > holds > > the data? (It does say Wr_zero can be used for secure erasure, > > but??) > > > > Good question for which I don't have any idea what the answer is, > > rick > > In both the above arguments, you are talking about specific > filesystem > implementation details that you'll also have to address with your new > operation. Actually, let me correct that... I'm not aware of any requirement on any of the NFSv4.2 operations or the NFSv4.2 extensions, that expect the permanent and irrevocable deletion of data. I definitely won't say there isn't a use case for it, but I am saying that it isn't covered by any NFS protocol today. IOW: if data wiping is what you're actually looking for here, then I think that needs to be a new operation, and we'll need a lot of discussion about how the NFS protocol should deal with all the various ways in which not just the storage, but also the filesystem go about trying to preserve data. We can probably leave the existence of external backups as an exercise for the user... 🤔️ -- Trond Myklebust Linux NFS client maintainer, Hammerspace trond.myklebust@xxxxxxxxxxxxxxx
