Re: Linux does not care for data integrity

Jeff Garzik
2005-06-02T01:55:18Z

Bill Davidsen wrote:
> 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.

Correct. That's the tradeoff with the ATA interface: you must be aware
of the cache flush requirements when designing a solution such as a
database that really cares about fsync(2), or a journalling filesystem.

> 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.

To make that possible, POSIX must become a transactional, async I/O
API... :)

Jeff