Host partition layout

XenServer 7.0 introduced a new host disk partition layout. By moving log files to a larger, separate partition, XenServer can store more detailed logs for a longer time. This feature improves the ability to diagnose issues. Simultaneously, the new partition layout relieves demands on Dom0’s root disk and avoids potential space issues due to log file disk space consumption. The new layout contains the following partitions:

  • 18 GB XenServer host control domain (dom0) partition

  • 18 GB backup partition

  • 4 GB logs partition

  • 1 GB swap partition

  • 0.5 GB UEFI boot partition

In XenServer 6.5 and earlier releases, the 4 GB control domain (dom0) partition was used for all dom0 functions, including swap and logging. Customers who do not use remote syslog or who used with third-party monitoring tools and supplemental packs found the size of the partition to be limited. XenServer eliminates this issue and provides a dedicated 18 GB partition to dom0. In addition, a larger partition dedicated to dom0 reduces demand on the dom0 root disk which can offer significant performance improvements.

The introduction of the 4 GB dedicated log partition eliminates scenarios where excessive logging filled up the dom0 partition and affected the behavior of the host. This partition also enables customers to retain a detailed list of logs for a longer time, improving the ability to diagnose issues.

The partition layout also contains a dedicated 500 MB partition required for UEFI boot.

Note:

If you install XenServer with the new partition layout described above, ensure that you have a disk that is at least 46 GB in size.

To install XenServer on smaller devices, you can do a clean installation of XenServer using the legacy DOS partition layout. A small device is one that has more than 12 GB but less than 46 GB disk space. For more information, see Installing on Small Devices.

Important:

We recommend that you allocate a minimum of 46 GB disk space and install XenServer using the new GPT partition layout.

Upgrade to the new partition layout

When upgrading to XenServer 7.6 from XenServer 6.5 or earlier version using XenCenter, the host partition layout is upgraded to the new layout, provided:

  • There is at least 46 GB of disk space on the local SR

  • There are no VDIs present on the local SR

  • You use XenCenter issued with XenServer 7.6 to perform a Rolling Pool Upgrade (RPU) to XenServer 7.6

    Warning:

    Customers cannot upgrade to the new host partition layout using xe CLI.

During the upgrade process, the RPU wizard checks for VDIs on the local SR. If there are any virtual disks (VDIs) present during the upgrade process, the wizard prompts you to move the VDI. Move VDIs on the local SR to a shared SR and then restart the upgrade process to continue with the new layout. If the VDIs cannot be moved or the local SR has insufficient space (less than 46 GB), the upgrade proceeds with the old partition layout. 0.5 GB of disk space is allocated from the dom0 partition to UEFI boot.

Restore the old partition layout

If you plan to restore XenServer from version 7.6 to version 6.x, the host partition layout reverts to the 6.x layout.

Legacy partition layouts

  • XenServer 5.6 Service Pack 2 and earlier used DOS partition tables to separate the root file system and backups from the local storage.

  • XenServer 6.0 introduced GUID partition tables to separate root file system, backup and local storage.

  • Installing XenServer 7.6 with disable-gpt on machines with a required initial partition that must be preserved, continues to use the DOS partitioning scheme. Upgrades from XenServer 5.x releases to 6.0 and then to 7.6 continue to use the existing DOS partitioning to retain any existing local storage.

The following table lists the installation and upgrade scenarios and the partition layout that is applied after these operations:

Operation Number of partitions before upgrade Number of partitions before installation/upgrade Partition table type  
Clean installation with at least 46 GB of primary disk space N/A 6 New GPT  
Clean installation with disable-gpt with a minimum of 12 GB of primary disk space N/A 3 (or 4 if there is a utility partition) DOS  
Upgrading from XenServer 6.x with VMs on local SR or with less than 46 GB of primary disk space 3 4 Old GPT  
Upgrading from XenServer 6.x without VMs on local SR or with more than 46 GB of primary disk space 3 6 New GPT  
Upgrading from XenServer 6.x DOS partition (and utility partition, if any) 3 (or 4 if there is a utility partition)   3 (or 4 if there is a utility partition) DOS

Host partition layout