> Thanks for thinking on this complicated issue. > > > > Most of the NAND flash devices and HDDs have wear leveling and bad sector > > replacement algorithms > applied. > > So I think that the life of the boot sector will not be exhausted first. > > I'm not too worried about the life of the boot-sector. > I'm worried about write failures caused by external factors. > (power failure/system down/vibration/etc. during writing) They rarely occur > on SD cards, but occur on > many HDDs, some SSDs and USB storages by 0.1% or more. Hard disk and SSD do not guarantee atomic write of a sector unit?
> Especially with AFT-HDD, not only boot-sector but also the following multiple > sectors become > unreadable. Other file systems will also be unstable on a such HW. > It is not possible to completely solve this problem, as long as writing to > the boot-sector. > (I think it's a exFAT's specification defect) The only effective way to > reduce this problem is to > reduce writes to the boot-sector. exFAT's specification defect... Well.. Even though the boot sector is corrupted, It can be recovered using the backup boot sector through fsck. > > > > Currently the volume dirty/clean policy of exfat-fs is not perfect, > > Thank you for sharing the problem with you. > > > > but I think it behaves similarly to the policy of MS Windows. > > On Windows10, the dirty flag is cleared after more than 15 seconds after all > write operations are > completed. > (dirty-flag is never updated during the write operation continues) > > > > Therefore, > > I think code improvements should be made to reduce volume flag records > > while maintaining the current > policy. > > Current policy is inconsistent. > As I wrote last mail, the problem with the current implementation is that the > dirty-flag may not be > cleared after the write operation.(even if sync is enabled or disabled) > Because, some write operations > clear the dirty-flag but some don't clear. > Unmount or sync command is the only way to ensure that the dirty-flag is > cleared. > This has no effect on clearing the dirty-flag after a write operations, it > only increases risk of > destroying the boot-sector. > - Clear the dirty-flag after every write operation. > - Never clear the dirty-flag after every write operation. > Unless unified to either one, I think that sync policy cannot be consistent. > > How do you think? > > > BR > --- > etsuhiro Kohada <kohada...@gmail.com>
