Xen on CentOS - Automating Installation-Administration
UNDER CONSTRUCTION
Introduction
This document assumes an functioning quattor environment and an installationserver with dhcp, tftp, and pxeboot.
Needed Tools
- Quattor [Quattor at nikhef]
- pypxeboot (on dom0s)
filesystem dom0
Quattor templates: /cfg/sites/ndpf/site/filesystems/*.tpl
!!! IMPORTANT: !!! * foresee a logvol with mount point /var/lib/xen/save which will take "Speicherabbilder" of running domUs, when the dom0 gets the reboot command, therefore it should be as large as available RAM + something (summ of all swap of domUs ?, see below) * give each domU not more than 512MB swap, if a domU excessively uses swap it will anyways got stuck.
Naming convention:
since the Filesystem layout depends on the hardware [how many hard disks 2-4, which raid (1 or 1-0)] and on the function in terms of xen-Dom0, xen-DomU, generic, ... I used the following scheme <hardware>-<function>.tpl The filesystem Template for our Dell-Power-Edge-1950 -function xen-Dom0 would then be: pe1950-x0.tpl
Virtualization considerations
- Dom0 (Host) needs < 10G for its system, tmp is not extensively used nor is var. To prevent the system to be unresponsive due to full / fs we could give 4GB /tmp and /var each and an extra volume for /var/lib/xen/save to take the files in which the state of the domUs are saved (roughly comparable to hybernate a running computer). These values can be smaller if we have hardware which has some disk space restrictions.
- For performance its best to limit the Memory of the dom0 to 512 MB and to prevent it from ballooning (i.e. takes all available memory)
- Dom0-swap should never happen, there are no processes that consume memory, if it swaps something went wrong, just in case we can try 1 GB swap
PE-1950 configuration
Hard disks: 2 X 500GB principle layout:
- Raid-1
- Primary Partitions
/boot 512MB /swap 4096MB
- LVM
Volumegroup System, Size: rest of available space I System-Volumes-Dom0 [/, /tmp] fs: ext3 II DomU-lvms added when needed
PE-2950 configuration
Hard disks: 4 X 500GB principle layout:hardware raid-10
- Primary Partitions
/boot 512MB /swap 4096MB
- LVM
Volumegroup System, Size: rest of available space
- System-Volumes-Dom0 [/, /tmp] fs: ext3
- DomU-lvms added when needed