NuKVM/xen-orchestra
3
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

feat(docs/load_balancing): add doc about VM anti-affinity mode (#5830)

Browse Source 
* feat(docs/load_balancing): add doc about VM anti-affinity mode

Signed-off-by: Ronan Abhamon <ronan.abhamon@vates.fr>

* grammar edits for anti-affinity

Co-authored-by: Jon Sands <fohdeesha@gmail.com>
This commit is contained in:
Ronan Abhamon 2021-06-30 10:37:25 +02:00 committed by GitHub
parent 3d15a73f1b
commit f095a05c42
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 18 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

BIN
docs/assets/antiaffinity.png Normal file
View File

Binary file not shown.
Side by Side

After

Width:  |  Height:  |  Size: 53 KiB

18
docs/load_balancing.md
View File

@ -94,3 +94,21 @@ The global situation (resource usage) is examined **every minute**.
:::tip
TODO: more details to come here
:::
## VM anti-affinity
VM anti-affinity is a feature that prevents VMs with the same user tags from running on the same host. This functionality is available directly in the load-balancer plugin.
This way, you can avoid having pairs of redundant VMs or similar running on the same host.
Let's look at a simple example: you have multiple VMs running MySQL and PostgreSQL with high availability/replication. Obviously, you don't want to lose the replicated database inside the VMs on the same physical host. Just create your plan like this:
![](./assets/antiaffinity.png)
- Simple plan: means no active load balancing mechanism used
- Anti-affinity: we added our 2x tags, meaning any VMs with one of these tags will never run on the same host (if possible) with another VM having the same tag
You can also use the performance plan with the anti-affinity mode activated to continue to migrate non-tagged VMs.
:::tip
This feature is not limited by the number of VMs using the same tag, i.e. if you have 6 VMs with the same anti-affinity tag and 2 hosts, the plugin will always try to place 3 VMs on each host. It will distribute as much as possible the VMs fairly and it takes precedence (in the majority of the cases) over the performance algorithm.
:::