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qm.adoc: style/grammar

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Fabian Grünbichler 2017-10-09 10:14:57 +02:00
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@ -170,7 +170,7 @@ either the *raw disk image format* or the *QEMU image format*.
thin provisioning of the disk image.
* the *raw disk image* is a bit-to-bit image of a hard disk, similar to what
you would get when executing the `dd` command on a block device in Linux. This
format do not support thin provisioning or snapshots by itself, requiring
format does not support thin provisioning or snapshots by itself, requiring
cooperation from the storage layer for these tasks. It may, however, be up to
10% faster than the *QEMU image format*. footnote:[See this benchmark for details
http://events.linuxfoundation.org/sites/events/files/slides/CloudOpen2013_Khoa_Huynh_v3.pdf]
@ -243,13 +243,13 @@ cost of context switches.
Resource Limits
^^^^^^^^^^^^^^^
Additional, to the count of virtual cores, you can configure how much resources
In addition to the number of virtual cores, you can configure how much resources
a VM can get in relation to the host CPU time and also in relation to other
VMs.
With the *cpulimit* (`Host CPU Time') option you can limit how much CPU time the
whole VM can use on the host. It is a floating point value representing CPU
time in percent, so `1.0` is equal to `100%`, `2.5` to `250%` and so on. If a
single process would fully use one single core he would have `100%` CPU Time
single process would fully use one single core it would have `100%` CPU Time
usage. If a VM with four cores utilizes all its cores fully it would
theoretically use `400%`. In reality the usage may be even a bit higher as Qemu
can have additional threads for VM peripherals besides the vCPU core ones.
@ -326,19 +326,19 @@ vCPU hot-plug
^^^^^^^^^^^^^
Modern operating systems introduced the capability to hot-plug and, to a
certain extent, hot-unplug CPU in a running systems. With Virtualisation we
have even the luck that we avoid a lot of (physical) problem from real
hardware.
But it is still a complicated and not always well tested feature, so its use
should be restricted to cases where its absolutely needed. Its uses can be
replicated with other, well tested and less complicated, features, see
certain extent, hot-unplug CPUs in a running systems. Virtualisation allows us
to avoid a lot of the (physical) problems real hardware can cause in such
scenarios.
Still, this is a rather new and complicated feature, so its use should be
restricted to cases where its absolutely needed. Most of the functionality can
be replicated with other, well tested and less complicated, features, see
xref:qm_cpu_resource_limits[Resource Limits].
In {pve} the maximal number of plugged CPUs is always `cores * sockets`.
To start a VM with less than this total core count of CPUs you may use the
*vpus* setting, it denotes how many vCPUs should be plugged at VM start.
*vpus* setting, it denotes how many vCPUs should be plugged in at VM start.
Currently only Linux is working OK with this feature, a kernel newer than 3.10
Currently only this feature is only supported on Linux, a kernel newer than 3.10
is needed, a kernel newer than 4.7 is recommended.
You can use a udev rule as follow to automatically set new CPUs as online in