Commit cbb533f4 authored by Raffa Santi's avatar Raffa Santi Committed by Thomas Thrainer
Browse files

Update NEWS and docs to document access switch

* Update NEWS file
* Update man page
* Update install.rst
Signed-off-by: default avatarSanti Raffa <>
Signed-off-by: default avatarThomas Thrainer <>
Reviewed-by: default avatarThomas Thrainer <>
parent 537dba0c
......@@ -7,6 +7,11 @@ Version 2.10.0 alpha1
New features
- KVM hypervisors can now access RBD storage directly without having to
go through a block device.
Incompatible/important changes
......@@ -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:
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
......@@ -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'.
If 'userspace', instances will access their disks directly without
going through a block device, avoiding expensive context switches
with kernel space and the potential for deadlocks_ in low memory
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 a "no such file or directory" error messages.
.. _deadlocks:
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
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