Question about file size 0 after filesystem recovery

[Peter Dufault]

> On Jan 5, 2021, at 13:49 , Charles Manning <cdhmanning at gmail.com> wrote:
> 
> What you get will depend very much on what file system you are using. Each file system has different behaviours.
> 
> If you have an application where you can yank power without a clean shutdown then it is advisable to use a file system with a more predictable caching policy.
> 
> For example, Yaffs (the file system I wrote) guarantees that the write has made it to media when the file is synced (fsync() and fdatasync() ) or closed.
> 
> If the file system's fsync()and close() only guarantee that that data is written into the block device's buffers then you have no guarantees.
> 

Yaffs is is associated with flash, and should be predictable, but in general you need to be concerned with disk caches.  Successful transfer to a disk doesn't mean the data is stored on the media.

I expect that's why the open group document specifies in the "RATIONALE" section that the conformance document should identify a way to identify how a file can be created in a manner that "fsync()" and "fdatasync()" are likely to work.

Peter
-----------------
Peter Dufault
HD Associates, Inc.      Software and System Engineering

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