Subj : Re: Move bookworm system from SSD to NVME To : bnl@nowhere.com From : Computer Nerd Kev Date : Sun Aug 04 2024 09:30:38 Bj?rn Lundin wrote: > looking at > > """ > The kernel keeps data in memory to avoid doing (relatively slow) disk > reads and writes. This improves performance, but if the computer > crashes, data may be lost or the file system corrupted as a result. sync > ensures that everything in memory is written to disk. > """ > > > So, what I think is that dd writes to a slow device, and it is cached by > the OS. > sync forces the OS to actually write to slow device. I've used the "conv=fsync" option to dd so that sync is done automatically. Since the man page is rather vague about it, I did a web search to double check that I wasn't imagining things and found this page which describes the behaviour with some examples: https://abbbi.github.io/dd/ > This may not be true with new and shiny fast NVM storage, but the > principle holds. The tests at that link were done with a RAM disk, and the kernel was caching writes to that, so it doesn't look like the caching system is smart enough to know when a device is fast enough that the cache isn't required. -- __ __ #_ < |\| |< _# --- SoupGate-Win32 v1.05 * Origin: Agency HUB, Dunedin - New Zealand | Fido<>Usenet Gateway (3:770/3) .