Re: Manual page for mount

[Phillip Susi]

I have always thought that the very name "sync" is completely 
misleading.  The option really has nothing at all to do with IO being 
synchronous or asynchronous, you can still perform IO either way ( think 
non blocking and linux async IO ).  What this option really does is 
simply cause the cache to switch to write-through mode instead of 
write-back mode.

I would have it say:

"All I/O to the file system should be synced to the disk immediately. 
This effectively changes kernel disk caching for the device from 
write-back to write-through mode, causing more writes to occur.  Media 
with limited write cycles, flash for example, will age prematurely. 
Many operations may be slowed down significantly by use of this option, 
but the filesystem will be more up to date in the event of a system crash."

Jonathan Andrews wrote:
> The "sync" and "async" options have an impact on disk caching, yet the
> manual pages avoid the term "cache" - I assume being careful to be
> general about capabilities of the underlying kernel.
>
> This does make it difficult for people trying to find options relating
> to disk cache behaviour, could the "sync" and "async" options be changed
> to refer to disk caches explicitly. 
>
>
> For example, sync currently reads.
>
> All I/O to the file system should be done synchronously. In case of
> media with limited number of write cycles (e.g. some flash drives)
> "sync" may cause life-cycle shortening.
>
>
> Something like this may be more meaningful to a lot of users, it may
> oversimplify things with the use of the term "cache", but in most cases
> its the reference users are looking (searching) for.
>
> "All I/O to the file system should be done synchronously. This
> effectively removes kernel disk caching for the device causing more
> writes to occur. Media with limited write cycles, flash for example,
> will age prematurely.
>
>
> Thanks,
> Jon