2 Virtualization scenarios #
Virtualization provides several useful capabilities to your organization: more efficient hardware use, support for legacy software, operating system isolation, live migration, disaster recovery, and load balancing.
2.1 Server consolidation #
Many servers can be replaced by one big physical server, so that hardware is consolidated, and guest operating systems are converted to virtual machines. This also supports running legacy software on new hardware.
Better usage of resources that were not running at 100%
Fewer server locations needed
More efficient use of computer resources: multiple workloads on the same server
Simplification of data center infrastructure
Simplifies moving workloads to other hosts, avoiding service downtime
Faster and agile virtual machine provisioning.
Multiple guest operating systems can run on a single host
Server consolidation requires special attention to the following points:
Maintenance windows should be carefully planned
Storage is key: it must be able to support migration and growing disk usage
You must verify that your servers can support the additional workloads
2.2 Isolation #
Guest operating systems are fully isolated from the host running them. Therefore, if there are problems inside virtual machines, the host is not harmed. Also, problems inside one VM do not affect other VMs. No data is shared between VMs.
UEFI Secure Boot can be used for VMs.
KSM should be avoided. For more details on KSM, refer to KSM.
Individual CPU cores can be assigned to VMs.
Hyper-threading (HT) should be disabled to avoid potential security issues.
VM should not share network, storage, or network hardware.
Use of advanced hypervisor features such as PCI pass-through or NUMA will adversely affect VM migration capabilities.
Use of paravirtualization and
virtiodrivers will generally improve VM performance and efficiency.
AMD provides some specific features regarding the security of virtualization.
2.3 Disaster recovery #
The hypervisor can make snapshots of VMs, enabling restoration to a known good state, or to any desired earlier state. Since Virtualized OSes are less dependent on hardware configuration than those running directly on bare metal, these snapshots can be restored onto different server hardware so long as it is running the same hypervisor.
2.4 Dynamic load balancing #
Live migration provides a simple way to load-balance your services across your infrastructure, by moving VMs from busy hosts to those with spare capacity, on demand.