We are very pleased to make the first beta of XenServer Dundee available to the community. As with all pre-release downloads, this can be found on the XenServer Preview page. This release does include some potential commercial features, and if you are an existing Citrix customer you can access those features using the XenServer Tech Preview. It’s also important to note that a XenServer host installed from the installer obtained from either source will have identical version number and identical functionality. Application of a Tech Preview license unlocks the potential commercial functionality. So with the „where do I get Dundee beta 1” out of the way, I bet you’re all interested in what the cool bits are, and what things might be worth paying attention to. With that in mind, here are some of the important platform differences between XenServer 6.5 SP1 and Dundee beta 1.

Updated dom0

The control domain, dom0, has undergone some significant changes. Last year we moved to a 64 bit control domain with a 3.10 kernel as part of our effort to increase overall performance and scalability. That change allowed us to increase VM density to 1000 VMs per host while making some significant gains in both storage and network performance. The dom0 improvements continue, and could have a direct impact on how you manage a XenServer.

CentOS 7

dom0 now uses CentOS 7 as it’s core operating system, and along with that change is a significant change in how „agents” and some scripts run. CentOS 7 has adopted systemd, and by extension so too has XenServer. This means that shell scripts started at system initialization time will need to change to follow the unit and service definition model specified for systemd.

cgroups for Control Isolation

Certain xapi processes have been isolated into Linux control groups. This allows for greater system stability under extreme resource pressure which has created a considerably more deterministic model for VM operations. The most notable area where this can be observed is under bootstorm conditions. In XenServer 6.5 and prior, starting large numbers of VMs could result in start operations being blocked due to resource contention which could result in some VMs taking significantly longer to start than others. With xapi isolation into cgroups, VM start operations no longer block as before resulting in VM start times being much more equitable. This same optimization can be seen in other VM operations such as when large quantities of VMs are shutdown.

RBAC Provider Changes

XenServer 6.5 and prior used an older version of Likewise to provide Active Directory. Likewise is now known as Power Broker, and XenServer is using the Power Broker Identity Services to provide authentication for RBAC. This has improved performance, scale and reliability, especially for complex or nested directory structures. Since RBAC is core to delegated management of a XenServer environment, we are particularly interested in feedback on any issues users might have with RBAC in Dundee beta 1.

dom0 Disk Space Usage

In XenServer 6.5 and prior, dom0 disk space was limited to 4GB. While this size was sufficient for many configurations, it was limiting for more than a few of you. As a result we’ve split dom0 disk into three core partitions; system, log and swap. The system partition is now 18GB which should provide sufficient for some time to come. This also means that the overall install space required for XenServer increases from 8GB to 46GB. As you can imagine, given the importance of this major change, we are very interested to learn of any situations where this change prevents XenServer from installing or upgrading properly.

Storage Improvements

Having flexible storage options is very important to efficient operation of any virtualization solution. To that end, we’ve added in support for three highly requested storage improvements; thin provisioned block storage, NFSv4 and FCoE.

Thin Provisioned Block Storage

iSCSI and HBA block storage can now be configured to be thinly provisioned. This is of particular value to those users who provision guest storage with a high water mark expecting that some allocated storage won’t be used. With XenServer 6.5 and prior, the storage provider would allocate the entire disk space which could result in a significant reduction in storage utilization which in turn would increase the cost of virtualization. Now block storage repositories can be configured with an initial size and an increment value. Since storage is critical in any virtualization solution, we are very interested in feedback on this functional change.


Fibre Channel over Ethernet is protocol which allows Fibre Channel traffic to travel over standard ethernet networks. XenServer now is able to communicate with FCoE enabled storage solutions, and can be configured at install time to allow boot from SAN with FCoE. If you are using FCoE in your environment, we are very interested in learning both any issues as well as learning what CNA you used during your tests.

Operational Improvements

Many additional system level improvements have been made for Dundee beta 1, but the following highlight some of the operational improvements which have been made.


XenServer 6.5 and prior required legacy BIOS mode to be enabled on UEFI based servers. With Dundee beta 1, servers with native UEFI mode enabled should now be able to install and run XenServer. If you encounter a server which fails to install or boot XenServer in UEFI mode, please provide server details when reporting the incident.

Automatic Health Check

XenServer can now optionally generate a server status report on a schedule and automatically upload it to Citrix Insight Services (formerly known as TaaS). CIS is a free service which will then perform the analysis and report on any health issues associated with the XenServer installation. This automatic health check is in addition to the manual server status report facility which has been in XenServer for some time.

Improved Patch Management in XenCenter

Application of XenServer patches through XenCenter has become easier. The XenCenter updates wizard has been rewritten to find all patches available on Citrix’s support website, rather than ones that have been installed on other servers. This avoids missing updates, and allows automatic clean-up of patches files at the end of the installation.

Why Participate in the Beta Program

These platform highlights speak to how significant the engineering effort has been to get us to beta 1. They also overshadow some other arguably core items like a move to the Xen Project Hypervisor 4.6, host support for up to 5TB of host RAM or even Windows guest support for up to 1TB RAM. What they do show is our commitment to the install base and their continued adoption of XenServer at scale. Last year we ran an incredibly successful prerelease program for XenServer Creedence, and its partly through that program that XenServer 6.5 is as solid as it is. We’re building on that solid base in the hopes that Dundee will better those accomplishments, and we’re once again requesting your help. Download Dundee. Test it in your environment. Push it, and let us know how it goes. Just please be aware that this is prerelease code which shouldn’t be placed in production and that we’re not guaranteeing you’ll ever be able to upgrade from it.

Download location: http://xenserver.org/prerelease

Defect database: https://bugs.xenserver.org

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