HOW TO SETUP A NEW HYPERVISOR
=============================

First make sure you understand how resalloc foniguration works (pools.yaml), and
that the referenced scripts (like 'libvirt-new' and 'vm-delete') can can
correctly identify the pool/hypervisor (those scripts likely need an update!) —
and thus assign (and later remove) appropriate IPv6 addresses, swap volumes,
etc.

Before the groups/copr-hypervisor.yml is run against the new host, manually
prepare the swap volume:

  1. disable the small zram swap (Fedora hypervisors)
        a) swapoff /dev/zram0
        b) dnf remove zram-generator-defaults
  2. remove old (small) swap, adjust this appropriately!
        a) swapoff /dev/mapper/vg_guests-LogVol01
        b) lvremove /dev/vg_guests/LogVol01
  3. create a larger SWAP volume
        a) lvcreate -L 300G vg_guests -n swap
        b) mkswap -L swap /dev/mapper/vg_guests-swap
        c) Note that this requires changing /etc/fstab, and then
           /etc/sysconfig/grub, and
        d) regenerating the /boot grub config
           $ grub2-mkconfig -o /boot/grub2/grub.cfg

Manually create space for volumes/images:

  1. assign the rest of the volume group to images
        a) lvcreate -n images -l 100%FREE vg_guests
        b) mkfs.ext4 /dev/mapper/vg_guests-images -L vmvolumes

Manually create the br0 interface:

  TODO: Not done by @praiskup but the infra team, TODO: add HOWTO


General VM requirements for builder VMs
---------------------------------------

- 2xvCPU+
- 4GB+ RAM
- 16G for built results => /var/lib/copr-rpmbuild
-  4G for the root / partition
- SWAP+RAM
  - 32GB tmpfs mountpoint for /var/cache/mock
  - 140GB+ SWAP for tmpfs for mock root(s) => /var/lib/mock

AMD hypervisors
===============

vmhost-x86-copr0[1-4].rdu-cc.fedoraproject.org

- 256G RAM
- 64 threads (2x16 cores, AMD EPYC 7302 16-Core Processor)
- 2.6T+ storage
- 300 G SWAP

This brings us 32+ (few devel) overcommitted builders on each builder:

 - 32*16G = up to 512 GRAM (256 RAM + 300 G SWAP)
 - 4G+16G = 20G*32 = up to 640G for root+results
 - 172G*32 = up to 5.5T SWAP for tmpfs (huge overcommit, though only limitted
   amount of build tasks require that much tmpfs)


Power8 hypervisors
==================

- 128G RAM


Power9 hypervisor
=================

vmhost-p09-copr01.rdu-cc.fedoraproject.org

- storage:
    ├─vg_guests-LogVol00 253:0    0     32G  0 lvm   /
    ├─vg_guests-swap     253:1    0    300G  0 lvm   [SWAP]
    └─vg_guests-images   253:2    0 1002.6G  0 lvm   /libvirt-images

- 256G RAM

- 160 threads
    - Thread(s) per core:  4
      Core(s) per socket:  20
      Socket(s):           2

- Let's take the risk, and overload by 32 + 1 stage.  So each of them has only
  about 32G storage.

Overall allocation:
    33*16G RAM => up to 528G used (256RAM + 300G SWAP can hold this)
    33*140G disk => 4TB+ ... about 400% overcommit in the worst case
    33*5 CPU = 165CPU used in the worst case
