When you run the 'fstrim' command on an ntfs-3g 2014.2.15 mountpoint
it says:

  fstrim: fstrim: /sysroot/: discard operation not supported.

I wonder if anyone has looked at how hard it would be to support this?
In the virt application I am writing it would make a massive
difference in performance if we are able to tell the hypervisor which
sectors are used and which are free.

fstrim is an ioctl (FITRIM).  I guess this ioctl would have to be
passed through fuse.  Latest fuse code doesn't mention fstrim or
FSTRIM at all, and the fuse FAQ mentions that ioctl() is not generally
supported (but maybe it's OK for specific cases?)

Then the ntfs-3g module would have to do something with that.  Does
ntfs-3g "know" precisely which sectors contain data and which are
unused, or is there some uncertainty about this because of the
undocumented nature of the disk format?

If this is not too hard I might have a go at it, but I don't want to
start something that you already know is not going to be possible for
some reason :-)

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
virt-df lists disk usage of guests without needing to install any
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http://people.redhat.com/~rjones/virt-df/

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