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Update load_balancing.md

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Olivier Lambert 2016-02-21 22:18:07 +01:00
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load_balancing.md
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@ -6,24 +6,56 @@ The goal here is to **distribute the VMs load** in the best way possible on your
Because Xen Orchestra is connected to [multiple pools](xo-server.md) and XenServer supports [live storage motion](https://www.citrix.com/content/dam/citrix/en_us/documents/products-solutions/storage-xenmotion-live-storage-migration-with-citrix-xenserver.pdf?accessmode=direct), we can make load balancing on a **whole XenServer infrastructure** (even between remote Data Centers).
## First challenges
A load balancing policy is called a "**plan**".
We are already capable to gather the metrics from all the hosts and VMs. But we need now to:
## Configure a plan
* analyze the global load
* detect bottlenecks
* compare to user limits
* act accordingly
In this coming new view, you'll be able to configure a new load balancing plan, or to edit an existing one.
There is also a lot of unknown parameters:
A plan has:
* a live storage motion could be very long on remote DC if your bandwidth is low
* avoid to made worse than no load balancing (this is easier than you think!)
* a name
* pool(s) where to apply the policy
* a mode (see paragraph below)
* a behavior (aggressive, normal, low)
### Plan modes
There is 3 modes possible:
* performance
* density
* mixed
#### Performance
VMs are placed to use all possible resources. This means balance the load to give the best overall performance possible. This tends to use all hosts available to spread the load.
#### Density
This time, the objective is to use less hosts as possible, and to concentrate your VMs. In this mode, you can choose to shutdown unused (and compatible) hosts.
#### Mixed
This mode allows you to use both performance and density, but alternatively, depending of a schedule. E.g:
* "performance" from 6:00 AM to 7:00 PM
* "density" from 7:01 PM to 5:59 AM
In this case, you'll have best of both when needed (energy saving during the night and performance during the day).
### Behavior
You can choose between "aggressive", "normal" and "low". This parameter will act on how the plan will activate migrations.
More aggressive it is, more it will make actions to follow the mode, comparing to short term metrics.
Less aggressive means actions only if older metrics confirm that migrating is necessary.
## More
The issue is [opened here](https://github.com/vatesfr/xo-web/issues/423).
## Steps
![](loadbalancer.jpg)
* `xo-analysis` get stats from `xo-server` and build reports/alerts
@ -31,6 +63,6 @@ The issue is [opened here](https://github.com/vatesfr/xo-web/issues/423).
* `xo-director` migrate VMs from various hosts (and even stop "useless" hosts)
## Resources
## External resources
The Citrix WLB Admin guide: http://docs.citrix.com/content/dam/docs/en-us/xenserver/xenserver-60/XenServer-6.0.0-wlb-userguide.pdf
Citrix WLB Admin guide: http://docs.citrix.com/content/dam/docs/en-us/xenserver/xenserver-60/XenServer-6.0.0-wlb-userguide.pdf