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new dfd01c4 Add info about performance with vm stats (#369)
dfd01c4 is described below
commit dfd01c4f86e2498e552f82d115d8c9db9d28220d
Author: Bryan Lima <[email protected]>
AuthorDate: Tue Dec 19 09:16:03 2023 -0300
Add info about performance with vm stats (#369)
Address apache/cloudstack#8364
---
source/adminguide/virtual_machines.rst | 19 ++++++++++++++++---
1 file changed, 16 insertions(+), 3 deletions(-)
diff --git a/source/adminguide/virtual_machines.rst
b/source/adminguide/virtual_machines.rst
index 1c0c6ad..620819c 100644
--- a/source/adminguide/virtual_machines.rst
+++ b/source/adminguide/virtual_machines.rst
@@ -1445,11 +1445,24 @@ Instance statistics are collected on a regular interval
(defined by global
setting vm.stats.interval with a default of 60000 milliseconds).
Instance statistics include compute, storage and Network statistics.
-Instance statistics are stored in the database as historical data for a
desired time period. These historical statistics then can be retrieved using
listVirtualMachinesUsageHistory API. For system VMs, the same historical
statistics can be retrieved using listSystemVmsUsageHistory API
+Instance statistics are stored in the database as historical data for a
desired time period. These historical statistics then can be retrieved using
``listVirtualMachinesUsageHistory`` API. For system VMs, the same historical
statistics can be retrieved using ``listSystemVmsUsageHistory`` API
-Instance statistics retention time in the database is controlled by the global
configuration - `vm.stats.max.retention.time`. Default value is 720 minutes,
i.e., 12 hours. Another global configuration that affects Instance statistics
is:
+Instance statistics retention time in the database is controlled by the global
configuration ``vm.stats.max.retention.time``, with a default value of 720
minutes, i.e., 12 hours. The interval in which the metrics are retrieved are
defined by the global configuration ``vm.stats.interval``, which has a default
value of 60,000 milliseconds, i.e., 1 minute. The default values are only meant
for guideline, as they can have a major impact in DB performance. The equation
below presents the over [...]
-- `vm.stats.user.vm.only` - When set to 'false' stats for system VMs will be
collected otherwise stats collection will be done only for user Instances.
+.. math::
+
+ StatsSize = (\frac{retention * 60000}{interval}) * nodes * VMs *
registrySize
+
+- **StatsSize**: the size, in `bytes`, required for storing the VM stats;
+- **retention**: the value of the configuration
``vm.stats.max.retention.time``;
+- **interval**: the value of the configuration ``vm.stats.interval``;
+- **nodes**: the number of nodes running the management server in the
environment;
+- **VMs**: the number of running VMs in the environment;
+- **registrySize**: the estimated size, in `bytes`, of the registry in the DB;
+
+Considering the default values of the configurations
``vm.stats.max.retention.time`` and ``vm.stats.interval``, three nodes running
the management server, 10,000 running VMs and an estimated registry size of 400
bytes, it would need, approximately, 8 GB of storage to store VM stats.
Therefore, the values for these configurations should be changed considering
the CloudStack environment, evaluating the required storage and its impact in
DB performance.
+
+Another global configuration that affects Instance statistics is
``vm.stats.user.vm.only``. When set to 'false' stats for system VMs will be
collected, otherwise stats collection will be done only for user Instances.
In the UI, historical Instance statistics are shown in the Metrics tab in an
individual Instance view, as shown in the image below.
