vSphere 4 and different storage types
Data storage is critical to virtualization, and vSphere supports several different data storage types including local storage using SCSI, SAS or SATA drives; network-based storage using iSCSI or NFS; and more expensive Fibre Channel (FC) data storage. To take advantage of many of vSphere's advanced features like VMotion and high-availability (HA), you should use a shared storage device. Fortunately iSCSI and NFS are both supported and provide affordable solutions that perform well enough as alternatives to Fibre Channel for all but the most intensive disk I/O workloads. vSphere has a software iSCSI initiator and NFS client built right into it so connecting to iSCSI or NFS storage targets is simple to set up. Also, vSphere supports using hardware iSCSI initiators with TCP/IP offload engines to reduce the CPU overhead on the host.
In addition, vSphere uses a special high-performance cluster file system called Virtual Machine File System (VMFS) that allows concurrent access by multiple host servers. VMFS volumes take away the backend storage complexities from the virtual machines (VMs) by presenting a single unified storage volume to them. One of vSphere's best storage features is thin provisioning, which makes more efficient use of disk space by growing a virtual disk and blocks are written to it instead of allocating it all at once when it is created. This allows you to overcommit your storage and take advantage of the often un-used disk space inside a guest VM's operating system. Some additional storage-related features of vSphere include the following:
- Fibre Channel over Ethernet (FCoE) support
- Jumbo frame support for iSCSI and NFS
- Ability to hot extend virtual disks
- Ability to grow VMFS volumes
- Storage paravirtualization
- VMDirectPath for VM direct I/O access
- vStorage APIs
vSphere 4 and networking
The vSwitch is the heat of a virtual nework, and vSphere has several options you can use based on your requirements. The simple standard vSwitch is easy to use, and provides fault tolerance and load-balancing across NICs. For larger environments that have many hosts and vSwitches, the vNetwork Distributed Switch lets you create global vSwitches to configure multiple hosts instead of configuring each host sepearately. vSphere can also support third-party vSwitches. Cisco's Nexus 1000v is the first virtual switch with vSphere support. This allows for tighter integration between the physical and virtual networks. All vSwitches in vSphere support advanced features such as VLAN tagging, NIC teaming and layer two security policies. Some additional network-related features of vSphere include:
- Support for IPv6 networks
- Support for private VLANs
- Support for Cisco Discovery Protocol (CDP)
- Support for network VMotion
vSphere 4 and high-availability
Virtualization is all about putting all your eggs in one basket, so maintaining high-availability is critical. If a single host fails, then all the VMs running on it will also fail, but vSphere includes features that can minimize or eliminate the amount of time that VMs are down due to a host failure. vSphere's high-availability feature allows VMs on shared storage to quickly be re-started on other hosts in the event that a host fails, minimizing downtime for the VMs. The fault tolerance (FT) feature takes this a step further and offers continuous availability by keeping a secondary VM on another host that is continuously updated in real-time using a Lockstep technique. This completely protects a virtual machine against a host hardware failure and results in zero downtime and data loss for the VM. While these features protect against unschuled hardware failures, there are also features that make planned maintenance easier. VMotion allows a running VM to move from one host to another on the same storage volume and Storage VMotion allows a running VM to move from one storage volume to another on the same host. These features let you perform maintenance on host hardware or storage devices without downtime.
vSphere 4 management
vSphere 4 also has tools for managing the virtual environment. The vSphere Client is a Windows application that serves as the primary management tool for vSphere. There is also a web user interface for managing virtual machines on ESX hosts (not ESXi) and command line management tools such as the vSphere CLI (vCLI) and the VMware Management Assistant (vMA). vCenter Server provides centralized management of hosts using the vSphere Client, and has features such as alarms, performance reporting, automation, and templates. Features such as high-availability, distributed resource scheduler (DRS) and VMotion require a vCenter Server. Multiple vCenter Servers can run in linked mode to provide centralized management of multiple virtual environments.
Ease of use
The vSphere hypervisor comes in two editions, ESX and ESXi. ESX has a larger footprint (1.7 GB) and a more complex Service Console that runs a full Linux OS. ESXi has a simpler management console, and smaller footprint (70 MB). As a result, ESXi can be installed in a few minutes and with almost no interaction. VMware also has a free service called VMware GO that helps users who are new to virtualization get up and running quickly. VMware's free Converter product and vCenter Server's Guide Consolidation feature also simplify virtualization by converting a physical server into virtual machines.
vSphere is a controlled and secure environment, and the hypervisor has never been compromised. vSphere's security is due in part to a set of security APIs called VMsafe that allows third-party applications to have tight integration for providing even better security controls. vSphere also includes a product called vShield Zones that provides a virtual firewall and IDS that can be used to provide better protection for virtual machines.
Data backup and data protection
vSphere has several data backup and recovery features that come with it. For example, virtual machine snapshots can be used to roll back to a previous virtual machine state. This feature is useful when patching guests or installing applications, so you can easily recover from any problems that may result. vSphere also includes a product called VMware Data Recovery (VDR) that can perform backups of virtual machines to any disk storage device using inline deduplication and compression. In addition, the vSphere APIs for data protection allow third-party backup applications to have tight integration for backing up and replicating virtual machines.
vSphere hosts and virtual machines scale well enough to allow almost any application or workload to be virtualized. With support for 1 TB of physical memory and 64 logical CPUs, vSphere hosts can support up to 256 running VMs per host. Plus, virtual machines can be assigned up to eight vCPUs and 255 GB of RAM to support even the most demanding applications. Using advanced memory techniques like transparent page sharing (TPS) and memory overcommitment, vSphere can allow more virtual machines to run with less physical resources.
Virtualization can help save money on power and cooling, but vSphere takes it even further with advanced features like Distributed Power Management (DPM) and Dynamic Voltage and Frequency Scaling (DVFS). DPM allows hosts to be automatically powered down and virtual machines migrated to other hosts during periods of low activity. When the resource demands increase, hosts are powered back on and VMs move back onto the hosts. DVFS allows host CPUs to dynamically change power states (p-states) when resource demands are low to reduce a host's energy consumption. CPU frequency and voltages are lowered and raised based on demand from virtual machines. When these two features are combined, it can help save money, especially in environments with regular extended periods of inactivity.
About this author: Eric Siebert is an IT industry veteran with over 25 years of experience covering many different areas but focusing on server administration and virtualization. He is a very active member in the Vmware Vmtn support forums and has obtained the elite Guru status by helping others with their own problems and challenges. He is also a Vmtn user moderator and maintains his own VMware VI3 information website, vSphere-land. In addition, he is a regular blogger and feature article contributor on TechTarget's SearchServerVirtualization and SearchVMware websites.
This was first published in May 2010