Re: [Gluster-devel] GlusterFS 3.0pre1 (Whats in 3.0)

[Gordan Bobic]

Anand Avati wrote:
> > > Key highlights of 3.0 are
> > > * Background self-healing: Applications won't be blocked any more during
> > healing operation.
> > > * Checksum based healing: Rsync like healing mechanism to heal only the
> > inconsistent blocks within a file.
> > > * Healing on the fly: Files can be healed even when the files are open and
> > application is performing active I/O.
> > > * Generation numbers: Self-healing can now reliably handle tricky corner
> > cases (such as "rm -rf" bug).
> >  Great list! I assume direct-io will be supported for virtualization as
> > well? The above and disable-direct-io are the last things keeping us from
> > launching Gluster on our Xen cluster.
>
> direct-io-mode for better write-performance is needed only on kernels
> < 2.6.27, and direct-io-mode is inharently incompatible with many
> other functionalities (like mmap, aio, running VMs). If you have a
> newer kernel, glusterfs-3.0 does not honor
> --disable/enable-direct-io-mode and always "works fast".

Is the detection based on kernel version or feature detection? The 
reason I ask is because there are heavily patched distro kernels like 
RHEL that are widely used, which nominally have a relatively low version 
number (2.6.18) but come with an awful lot of patches and features 
(1000+ by now IIRC) that add functionality from recent kernels?

Gordan