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Virtuozzo 7 Beta Readme

Virtuozzo Overview

Virtuozzo is a bare-metal virtualization solution that includes container virtualization, KVM-based virtual machines, software-defined storage along with enterprise features and production support. It runs on top of Virtuozzo Linux, a RHEL-based Linux distribution.

The key changes in Virtuozzo 7 are as follows:

  • Virtuozzo 7 is based on RHEL 7 and Kernel 3.10+.

  • Virtuozzo 7 uses the KVM/QEMU hypervisor.

  • Containers use cgroups and namespaces that limit, account for, and isolate resource usage as isolated namespaces of a collection of processes. The beancounters interface remains in place for backward compatibility. At the same time, it acts as a proxy for actual cgroups and namespaces implementation.

  • UUIDs are used to identify both virtual machines and containers. With containers, prlctl treats the former VEID parameter as name.

  • VCMMD, the fourth-generation unified memory manager, and vcmmd, a single daemon for managing memory of both virtual machines and containers. Virtuozzo 7 uses memcg. Balancing and configuring memcg limits enables getting the exact overcommit, shadow gangs, swap, page cache overuse Virtuozzo parameters.

What’s New in This Beta

This beta introduces virtual machines functionality, a new hypervisor, a new virtual machine HDD image format, guest tools, a number of improvements to the memory manager that benefit both containers and virtual machines.

  • Virtuozzo 7 uses the KVM/QEMU hypervisor and enables customers to manage virtual machines via the libvirt API and VirtManager.

  • Virtual machine HDD images are stored in the QCOW2 format.

  • Virtuozzo provides guest tools for virtual machines that currently allow the following: to execute commands in VMs from the host, to set user passwords, to set and obtain network settings, to change SIDs, to enter VMs.

  • Autoballooning (technical preview). This beta features a technical preview of autoballooning for virtual machines. Before this release, overcommitted virtual machine memory was reclaimed by means of swapping. Now a much more efficient technique can be used: vcmmd determines which virtual machines do not use their RAM actively and reclaims it by inflating a balloon inside every such VM. Autoballooning also provides benefits to mixed container/VM environments.

  • Memory guarantees. A memory guarantee is a percentage of container or virtual machine’s RAM that said container or VM is guaranteed to have. For virtual machines, the memory guarantee value is set to 40% by default; For containers, the default memory guarantee value is 0%. To change the default value, use the new prlctl set --memguarantee command.

  • Memory hotplugging. The new and improved memory hotplugging techique allows both increasing and reducing virtual machine RAM size on the fly, without the need to reboot the VM. Configured by the command prlctl --mem-hotplug, memory hotplugging is implemented as a combination of ballooning and addition/removal of virtual DIMM slots. When a command to increase VM memory size is run, the memory is first expanded by deflating the VM’s balloon. If fully deflating the balloon is not enough to get the requested memory size, virtual DIMM slots are added. When a command to reduce VM memory size is run, the memory is shrunk by inflating the VM’s balloon. This feature is disabled by default and only supported for virtual machines with at least 1GB of RAM.

  • Kernel same-page merging. To optimize memory usage by virtual machines, Virtuozzo uses a feature of Linux called Kernel Same-Page Merging (KSM). The KSM daemon ksmd periodically scans memory for pages with identical content and merges those into a single page. Said page is marked as copy-on-write (COW), so when its contents are changed by a virtual machine, the kernel creates a new copy for that virtual machine. KSM enables the host to: avoid swapping due to merging of identical pages, run more virtual machines, overcommit virtual machine memory, and speed up RAM and hence certain applications and guest operating systems.

  • Cloning of virtual machines.

  • Renaming of virtual machines.

  • Setting of CPU affinity masks for virtual machines.

  • LVM support in prl_disk_tool. The prl_disk_tool can now resize/compact images with LVM.

  • In-place resizing of virtual machine disks.

  • Hotplugging of virtual machine disks.

Known Issues and Restrictions

  • Limited simfs support (feature provided as is). (OVZ-6581, OVZ-6613) Unlike OpenVZ, the simfs layout is based on bindmounts in Virtuozzo 7. When a simfs-based container is started, its private area is bindmounted to the root container area. To create a simfs container: 1) Set VEFSTYPE=simfs in /etc/vz/vz.conf, 2) Run vzctl create <CT_name>. The simfs limitations in Virtuozzo 7 are: 1) No support for first- or second-level quotas, 2) No support for online migration of simfs-based containers.

  • Online and offline VM migration is supported as a proof of concept and may fail frequently. (PSBM-40084, PSBM-43767)

  • CPU limits for VMs work differently compared to Virtuozzo 6. Certain features like limits in MHz are not implemented. (PSBM-40823)

  • EFI virtual machines are not supported. (PSBM-40704)

  • In Windows VMs, each new SCSI HDD may be added as offline. As a workaround, you can either bring each disk back online manually. Alternatively, before the first boot with a new disk, run san policy=onlineall in DISKPART to set the SAN policy to OnlineAll. (PSBM-41663)

  • Guest tools information may not be available for a VM with the guest tools installed until guest tools state is retrieved (e.g., by running prlctl list -i). (PSBM-44235)

  • No connectivity between VM and external host on the same host-routed network IP subnet. (PSBM-44285)

  • Passwords with double quotes are not supported for virtual machines and containers. (PSBM-44576)

  • Host CD-ROM cannot be added to a VM. (PSBM-44773)

  • Private networks are not supported.

  • Basic Firewall is not supported.

  • Virtual Automation and Virtual Automation Agent are not supported.

  • Shared Folders functionality may not work.

Dropped Functionality

  • VZFS

  • Delayed /vz mounting

  • Commands prlctl --memquota, prlsrvctl --mem-limit.

  • The vzbackup, vzabackup, and pbackup utilities. For more information, see http://kb.virtuozzo.com/119017.

  • Migration of physical servers to Containers and migration of Xen virtual machines to virtual machines. For more information, see http://kb.virtuozzo.com/119016.

  • Start-As-User.

  • Shared smartcard (CCID) support.

  • The global iptables mask configured in /etc/sysconfig/vz.

  • All UBC resources except physpages and swappages.

  • The vziptables parameter configured in the kickstart file used for unattended installations of Virtuozzo.