When running CentOS 6.5 as a KVM host, a full GNOME desktop typically consumes:

• ~300-500MB RAM when idle
• 1-2% CPU overhead for basic compositing
• Additional disk I/O for logging and temp files

These numbers spike when actively using GUI tools. A quick test on my E5-1650 test box:

# Before GUI install
free -m
              total used free
Mem:         32024  872 31151

# After GNOME install + idle
              total used free
Mem:         32024 1422 30601

While virsh handles 90% of VM operations, these GUI tools provide unique value:

virt-manager          # Complete VM lifecycle management
virt-viewer           # SPICE/VNC console with clipboard sharing
virt-install --graphics vnc # Graphical installer for complex OS setups

Example workflow for creating a Windows VM with virt-manager:

1. Click "New VM" wizard
2. Drag CPU/memory sliders visually
3. Attach ISO via file browser
4. Monitor installation via embedded console

Instead of full GNOME, consider these alternatives:

# X11 + Fluxbox (lightest option)
yum groupinstall "X Window System"
yum install fluxbox xterm virt-manager

# Or LXDE (middle ground)
yum groupinstall "LXDE Desktop"
yum install virt-manager

# Remote X forwarding (no local GUI)
ssh -X root@server virt-manager

For headless servers with occasional GUI access:

# Install only required components
yum --setopt=group_package_types=optional groupinstall "Desktop Platform"
yum install virt-manager dejavu-sans-fonts

# Enable VNC for remote management
vim /etc/libvirt/qemu.conf
# Add:
vnc_listen = "0.0.0.0"

Then access from any machine with TigerVNC or Remmina.

Testing identical VM workloads:

The overhead becomes more noticeable when running memory-constrained VMs.

# virt-manager specific features:
- Drag-and-drop VM console management
- Visual disk allocation mapping
- Real-time performance graphs
- SPICE protocol configuration GUI

# Fluxbox (ultra-lightweight):
yum groupinstall "X Window System"
yum install fluxbox xterm

# LXDE core components:
yum --skip-broken install lxde-common lxsession openbox

# Xfce minimal:
yum --exclude=*office* --exclude=*firefox* install @xfce

# Disable GNOME animations:
gconftool-2 --set /desktop/gnome/interface/enable_animations --type bool false

# Reduce services:
chkconfig abrtd off
chkconfig avahi-daemon off
chkconfig gdm off

# Use VNC instead of local display:
vncserver :1 -geometry 1280x800 -depth 16