4 ms·
This works at higher levels of abstraction, too. For instance, NetApp filers have a deduplication feature, where identical files are detected and stored once in
by _yosefk 10y ago
This works at higher levels of abstraction, too. For instance, NetApp filers have a deduplication feature, where identical files are detected and stored once instead of several times. When one of the files is changed, supposedly a copy on write happens. Yet in practice, I saw, more than once, two identical files, with completely identical time stamps, owned by two different users, where only one file was modified intentionally by a program ran by one of the users (that program logged its actions to a file, and the other user's log would be empty, plus there was no chance that both modified their files at the exact same time.) I concluded that NetApp's deduplication wasn't on the beaten path - or perhaps something in the timing or other specifics of our creation and modification of identical files was unusual.
- tw04 10y agoThe first problem with your example is that NetApp deduplication occurs at the block level, not the file level. The second problem is, given the number of systems in the field utilizing it - if your example were accurate there would be literally THOUSANDS of people up in arms. Furthermore, their deduplication is post-process, so even if dedup were to somehow modify atime, which it doesn't, you wouldn't have seen the access time change for at best 24 hours after the file was modified. Troll on.
- _yosefk 10y agoThen it wasn't deduplication. I swear it was a NetApp file server, two files, one modified by a program that logged the change, the other getting the same bits as the first, the time stamps were completely identical. Dedup was just a guess.