Thanks all,
On Sun, Mar 30, 2014 at 9:59 PM, <[email protected]> wrote: > On Sat, 29 Mar 2014 18:17:52 +0530, Sankar P said: > > > However, there is no guarantee that the data will be actually written > > to disk. I have heard instances where a caching layer in the disk > > tells the filesystem that the data is written but the data was not > > written and there was a power failure and an ensuing loss of data. > > Actually, let me go a step further - I know of no current disks which > support write caching that *don't* lie to the OS and say "I/O complete, > data is on the disk" when it lands in the cache (leaving you vulnerable > if there's a power hit before it flushes the cashe). > > Even more evil - although you'd *think* that the solution is to just > disable > the write cache so the disk can't lie and has to wait for the data to hit > the platters, that's not quite true. There's been disks (especially on the > very low end where they Just Don't Care, and on the high end were numbers > are everything) that will *say* they disabled the write cache, but it's > still > doing it inside.... > Though I can't be still sure of that the data has been flushed to disk something like wait_on_buffer() will help me a bit I am still curious to know what happens in journalling, as the journal NEEDS to be committed to the disk, before data writes/modifcation proceed. Same for Direct IO as Vineet Suggested I could not look at the code, will look the code. -- Regards, Rishi Agrawal
_______________________________________________ Kernelnewbies mailing list [email protected] http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
