Il 03/10/2012 19:58, Anand Avati ha scritto:
I think these 3 lines should be removed. We're bypassing the host
buffer cache just by virtue of using a userspace driver, and that's what
cache=none cares about.
O_DIRECT also has an effect on the behavior of the "client side" (the
part within the qemu) of Gluster stack as well. I presume the intention
of O_DIRECT is to minimize use of memory (whether as host' page cache or
buffered data in user space). To that end it is a good idea to leave
O_DIRECT flag set.
The behavior of whether gluster bricks need to get the O_DIRECT
propagated or not is a different issue. We are exploring the possibility
of not sending O_DIRECT flag over the wire to mimic NFS behavior. That
would be independent of the qemu block driver setting the open flag.
What is the effect of O_DIRECT on the client exactly?