Re: Linux does not care for data integrity

Bill Davidsen
2005-06-02T01:38:52Z

Jeff Garzik wrote:

> Bill Davidsen wrote:
>
>> This would change the meaning of fsync from "force out the data" to
>> "wait for the data to be written" in some implementations.
>
>
> This is the meaning of fsync: copies all in-core parts of a file to
> disk, and waits until the device reports that all parts are on stable
> storage.
>
> Anything less is a bug.

How about anything more? The truth is that much common hardware doesn't
really make the cache to disk move visible, and turning off cache really
hurts performance. And it would appear that fsync force a lot more data
out of memory than just the blocks for the file in question.

However, the point I was making is that it would be useful to be able to
tell when the write to non-volatile took place, not to force that to
happen. Not to do anything which would flush a lot of other stuff and
busy the drive. What I suggest is NOT fsync, just a way to assure ordering.

--
bill davidsen <davidsen@tmr.com>
CTO TMR Associates, Inc
Doing interesting things with small computers since 1979