Is persistant preallocation possible?

[Nathan Scott]

----- "Jeff Zheng" <Jeff.Zheng at endace.com> wrote:

> Hi,
> 
> We are trying to control where the files are being allocated on the
> disks, and we tried xfs preallocation. What we found is that each time
> the file being reopened the location of the pre-allocated space could
> change (not all the time). Is there a way to do persistent
> preallocation in xfs, like the same file will always be on the same
> location on the disk given that the requested size doesn’t change?
> 

Sounds like you are truncating the file (on open?), and hence discarding
the preallocation.  XFS preallocation is persistent already, so I think
something you are doing must be discarding those preallocated extents.

Could you post a test program, or sequence of xfs_io commands, that would
demonstrate the problem?

cheers.

-- 
Nathan