I reworded some parts (for example, we don't "mount" block devices). I'll apply that before pushing.
LGTM, thanks. On Wed, Oct 2, 2013 at 11:02 AM, Raffa Santi <[email protected]> wrote: > * Update man page > * Update install.rst > > Signed-off-by: Raffa Santi <[email protected]> > --- > NEWS | 5 +++++ > doc/install.rst | 25 +++++++++++++++++++++++++ > man/gnt-cluster.rst | 15 +++++++++++++++ > 3 files changed, 45 insertions(+) > > diff --git a/NEWS b/NEWS > index 5673d7a..e1d4de9 100644 > --- a/NEWS > +++ b/NEWS > @@ -7,6 +7,11 @@ Version 2.10.0 alpha1 > > *(unreleased)* > > +New features > +~~~~~~~~~~~~ > +- KVM hypervisors can now access RBD storage directly without having to > + mount a block device. > + > Incompatible/important changes > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > diff --git a/doc/install.rst b/doc/install.rst > index 04ea7c0..2b4551a 100644 > --- a/doc/install.rst > +++ b/doc/install.rst > @@ -367,6 +367,31 @@ above. We recommend using the latest version of > ``ceph-common``. > > $ apt-get install ceph-common > > +KVM userspace access > +~~~~~~~~~~~~~~~~~~~~ > + > +If your cluster uses a sufficiently new version of KVM (you will need at > +least QEMU 0.14 with RBD support compiled in), you can take advantage of > +KVM's native support for ceph in order to have better performance and > +avoid potential deadlocks_ in low memory scenarios. > + > +.. _deadlocks: http://tracker.ceph.com/issues/3076 > + > +To initialize a cluster with support for this feature, use a command > +such as:: > + > + $ gnt-cluster init \ > + --enabled-disk-templates rbd \ > + --ipolicy-disk-templates rbd \ > + --enabled-hypervisors=kvm \ > + -D rbd:access=userspace > + > +(You may want to enable more templates than just ``rbd``.) > + > +You can also change this setting on a live cluster by giving the same > +switches to ``gnt-cluster modify``, or change those settings at the node > +group level with ``gnt-group modify``. > + > Configuration file > ~~~~~~~~~~~~~~~~~~ > > diff --git a/man/gnt-cluster.rst b/man/gnt-cluster.rst > index 3b0ee1c..8643710 100644 > --- a/man/gnt-cluster.rst > +++ b/man/gnt-cluster.rst > @@ -469,6 +469,21 @@ pool > When a new RADOS cluster is deployed, the default pool to put rbd > volumes (Images in RADOS terminology) is 'rbd'. > > +access > + If 'userspace', instances will try to access their disks > + directly without first mounting them to block devices, avoiding > + expensive context switches with kernel space and the potential > + for deadlocks_ in low memory scenarios. > + > + The default value is 'kernelspace' and it disables this behaviour. > + This setting may only be changed to 'userspace' if all instance > + disks in the affected group or cluster can be accessed in userspace. > + > + Attempts to use this feature without rbd support compiled in KVM > + result in "no such file or directory" error messages. > + > +.. _deadlocks: http://tracker.ceph.com/issues/3076 > + > The option ``--maintain-node-health`` allows one to enable/disable > automatic maintenance actions on nodes. Currently these include > automatic shutdown of instances and deactivation of DRBD devices on > -- > 1.7.10.4 > > -- Thomas Thrainer | Software Engineer | [email protected] | Google Germany GmbH Dienerstr. 12 80331 München Registergericht und -nummer: Hamburg, HRB 86891 Sitz der Gesellschaft: Hamburg Geschäftsführer: Graham Law, Christine Elizabeth Flores
