I am pleased to announce that Dundee beta 3 has been released, and for those of you who monitor Citrix Tech Previews, beta 3 corresponds to the core XenServer platform used for Dundee TP3. This third beta marks a major development milestone representing the proverbial „feature complete” stage. Normally when announcing pre-release builds, I highlight major functional advances but this time I need to start with a feature which was removed.
Thin Provisioned Block Storage Removed
While its never great to start with a negative, I felt anything related to removal of a storage option takes priority over new and shiny. I’m going to keep this section short, and also highlight that only the new thin provisioned block feature was removed and existing thin provisioned NFS and file based storage repositories will function as they’ve always done.
What should I do before upgrading to beta 3?
While we don’t actively encourage upgrades to pre-release software, we do recognize you’re likely to do it at least once. If you have built out infrastructure using thin provisioned iSCSI or HBA storage using a previous pre-release of Dundee, please ensure you migrate any critical VMs to either local storage, NFS or thick provisioned block storage prior to performing an upgrade to beta 3.
So what happened?
As is occasionally the case with pre-release software not all features which are previewed will make it to the final release; for any of a variety of reasons. That is of course one reason we provide pre-release access. In the case of the thin provisioned block storage implementation present in earlier Dundee betas, we ultimately found that it had issues under performance stress. As a result, we’ve made the difficult decision to remove it from Dundee at this time. Investigation into alternative implementations are underway, and the team is preparing a more detailed blog on future directions.
Beta 3 Overview
Much of difference between beta 2 and beta 3 can be found in some of the details. dom0 has been updated to a CentOS 7.2 userspace, the Xen project hypervisor is now 4.6.1 and the kernel is 3.10.96. Support for xsave and xrestor floating point instructions has been added, enabling guest VMs to utilize AVX instructions available on newer Intel processors. We’ve also added experimental support for the Microsoft Windows Server 2016 Tech Preview and the Ubuntu 16.04 beta.
Beta 3 Bug Fixes
Earlier pre-releases of Dundee had an issue wherein performing a storage migration of a VM with snapshots and in particular orphaned snapshots would result in migration errors. Work has been done to resolve this, and it would be beneficial for anyone taking beta 3 to exercise storage motion to validate if the fix is complete.
One of the focus areas for Dundee is to improve scalability, and as part of that we’ve uncovered some situations where overall reliability wasn’t what we wanted. An example of such a situation, which we’ve resolved, occurs when a VM with a very large number of VBDs is running on a host, and a XenServer admin requests the host to shutdown. Prior to the fix, such a host would become unresponsive.
The default logrotate for xensource.log has been changed to rotate at a 100MB in addition to daily. This change was done as on very active systems excessive disk consumption could result in the prior configuration.