Re: [Firebird-devel] FB 2.1 64bit and memory usage ??

[Vlad H. <hv...@us...>]

> Hi,
> 
> A few months ago, I learned that the disk drive industry
> association, IDEMA, approved their new Long Block Data (LBD)
> sector standard. The LBD spec. increases the standard sector
> size from 512 bytes to 4096 bytes.
...
> My concern: the new sector standard may impact direct I/O
> alignment constraints for I/O buffers, transfer sizes and file
> offsets, depending on the implementation of direct I/O used.

    We not allow database page size less than 4KB since FB 2.1
Old databases may still use small pages however

...
> I know various db "vendors" support direct I/O as a db option
> on Linux, using the current O_DIRECT implementation, but they
> had to be careful in their code to avoid certain O_DIRECT
> kernel bugs and race conditions.  For example, it seems mixing
> O_DIRECT and non-O_DIRECT reads and writes on the same file
> simultaneously may result in stale data reads or writes. The
> workaround: don't do that!

    posix_fadvise free from this drawback and not restrict us to use 
aligned memory buffers, right ?
 
> I suspect that the FB's direct I/O option on linux is going to
> need a lot of testing.  ;-)

    As it may be disabled (and will be disabledby default) i see no 
problem with it.

    As for testing - are you taker ? :)

Regards,
Vlad