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Josh Siviour
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* docs: bring doc titles and descriptions into SEO length limits Rewrite the frontmatter title and description of every published doc so the rendered <title> lands in 50-60 characters (including the site suffix) and the meta description lands in 150-160 characters. * docs: move SEO titles to a seoTitle field and restore display titles The frontmatter title renders as the page H1 and the sidebar label, so tuning it for the title tag shortened nothing and lengthened the visible navigation. Put the search-facing string in seoTitle and give title back its original value.
124 lines
3.1 KiB
Markdown
124 lines
3.1 KiB
Markdown
---
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title: "Placement Groups"
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seoTitle: "AWS EC2 Placement Groups on Spinifex — Spinifex Docs"
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description: "Create and manage spread and cluster placement groups to control how Spinifex places EC2 instances across physical hosts for fault isolation or low latency."
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category: "Compute"
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tags:
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- ec2
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- placement
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- spread
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- cluster
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resources:
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- title: "Spinifex Repository"
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url: "https://github.com/mulgadc/spinifex"
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- title: "AWS Placement Groups"
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url: "https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/placement-groups.html"
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---
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# Placement Groups
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> Create and manage spread and cluster placement groups for hardware-level instance placement control.
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## Table of Contents
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- [Overview](#overview)
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- [Create](#create)
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- [Launch Into a Placement Group](#launch-into-a-placement-group)
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- [Describe](#describe)
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- [Delete](#delete)
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- [Troubleshooting](#troubleshooting)
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- [InsufficientInstanceCapacity Error](#insufficientinstancecapacity-error)
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- [Cannot Delete Placement Group](#cannot-delete-placement-group)
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---
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## Overview
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Placement groups control how Spinifex distributes instances across physical hosts. Two strategies are supported:
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- **Spread** — One instance per physical host, maximising fault isolation
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- **Cluster** — All instances on the same host, minimising latency
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The `partition` strategy is not supported.
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**Supported operations:**
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- `create-placement-group` — Create a new group
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- `describe-placement-groups` — Query groups with optional filters
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- `delete-placement-group` — Remove an empty group
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## Instructions
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## Prerequisites
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- A running Spinifex cluster (see [Setting Up Your Cluster](/docs/setting-up-your-cluster))
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- AWS CLI configured with the `spinifex` profile:
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```bash
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export AWS_PROFILE=spinifex
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```
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## Create
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```bash
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aws ec2 create-placement-group \
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--group-name my-spread-group \
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--strategy spread
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```
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```bash
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aws ec2 create-placement-group \
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--group-name my-cluster-group \
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--strategy cluster
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```
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## Launch Into a Placement Group
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```bash
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aws ec2 run-instances \
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--image-id $SPINIFEX_AMI \
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--instance-type t3.small \
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--key-name spinifex-key \
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--placement GroupName=my-spread-group \
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--count 3
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```
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## Describe
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```bash
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aws ec2 describe-placement-groups
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aws ec2 describe-placement-groups --group-names my-spread-group
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aws ec2 describe-placement-groups --group-ids pg-abc123
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aws ec2 describe-placement-groups \
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--filters Name=strategy,Values=spread
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```
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## Delete
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The group must have no running instances before it can be deleted:
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```bash
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aws ec2 terminate-instances --instance-ids $INSTANCE_ID
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aws ec2 delete-placement-group --group-name my-spread-group
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```
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## Troubleshooting
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### InsufficientInstanceCapacity Error
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Not enough distinct physical hosts for a spread launch. Reduce `--count` or terminate existing instances to free host slots:
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```bash
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spx admin nodes list
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```
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### Cannot Delete Placement Group
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The group still has running instances. Terminate them first:
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```bash
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aws ec2 describe-instances \
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--filters Name=placement-group-name,Values=my-spread-group
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aws ec2 terminate-instances --instance-ids $INSTANCE_ID
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```
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