By Francis Chu  |  Posted 2004-03-15 Print this article Print

VirtualCenter is the first VM (virtual machine) resource manager from VMware, which was acquired in December by EMC Corp. VirtualCenter currently works only with VMwares ESX Server, Version 2.0 or higher. Prices for VirtualCenter start at $5,000 for the management server and $300 per CPU in the managed ESX host. ESX Server 2.0 costs $3,750 for a two-CPU server. Both ESX Server 2.0 and VirtualCenter shipped late last year.

ESX Server 2.0 provides mainframe-class native hardware virtualization for enterprise applications. ESX Server transforms physical server systems into virtual resource partitions, operating systems and applications. Hardware resources such as CPU cycles and memory are allocated dynamically based on VM needs. ESX runs directly on server hardware without the need for a host operating system; this provides better resource utilization and less overhead than VMwares midrange GSX Server.

ESX Servers guest operating system support includes Linux, Windows and NetWare, but its breadth of support is not as great as that of GSX Server. Unlike GSX Server, however, ESX Server supports symmetric multiprocessing within VMs, allowing more flexible resource allocation.

VirtualCenter uses a distributed architecture wherein several components make up the overall management system. VirtualCenter comprises the management server service, a database, VM templates, a management client and the VM agents.

The VM templates allow users to save VM settings for quicker deployment. The management server service controls all communications with the VM hosts and can be installed on systems running state Windows 2000 Server/ Advanced Server, Windows Server 2003 or Windows XP. The database maintains inventory and VM information; supported databases include Oracle Corp.s Oracle and Microsoft Corp.s SQL Server 2000 and Access.

IT managers can run the server service, database and management client on separate server systems or VMs for more flexibility in distributed environments or across different data centers. Integration with Microsofts Active Directory enables IT managers to delegate granular access permissions to VMs and ESX Server hosts easily.

However, VirtualCenters hardware requirements are not insignificant: The minimum hardware configuration for Virtual Center is an Intel Corp. 2MHz Pentium 4, 1GB of memory and Gigabit Ethernet. In addition, to take advantage of the optional VMotion technology, a SAN (storage area network) back end is required.

eWEEK Labs tested VirtualCenters provisioning and dynamic resource management capabilities using the testing infrastructure at VMwares lab in Palo Alto, Calif.

The testing environment consisted of three main host machines running ESX Server 2.0. Each ESX host also had a direct connection to a Hewlett-Packard Co. StorageWorks Modular Smart Array 1000, a midrange SAN system that provided the storage back end for the VM images.

During tests, the VirtualCenter interface allowed us to view VM status, hardware performance and alerts easily, and we could launch a remote console from the VirtualCenter interface to control VMs. We could drag and drop VMs from one ESX Server host to another from within the interface, and wizards guided us quickly through the configuration steps.

We also tested VMwares unique VMotion technology, which costs $700 more per CPU managed. VMotion copies the entire system and memory state of a VM while it is running, with minimal interruption to the applications and services that are running on the VM.

VMotion maintains the state of the memory pages as VM data is being transferred; once the migration is completed, the source VM is suspended, the memory pages are copied and the new VM resumes on the target ESX Server host.

VMotion manages the MAC (media access control) address during migration to maintain the network identity of the VM. VMotion will ping the network router to ensure the new virtual MAC address is updated.

VMotion works well with TCP applications and services that have an application buffer or a tolerance for network delays. Administrators should carefully consider VMotions use with mission-critical applications. However, in our tests, we found latency to be negligible for applications such as SQL database transactions and almost non-existent for Microsofts Windows Media Services. During tests using VMotion, we experienced latency of less than 2 seconds; in most cases, the migration will be transparent to users.

IT managers should be aware of a potential shortcoming: VMotion will work only when migrating VMs between physical systems that have CPUs within the same processor family (that is, between machines with Pentium 4 processors but not between a Pentium III and a Pentium 4 system). This hardware requirement applies only to the processor family and is independent of processor speed.

Technical Analyst Francis Chu is at francis_chu@ziffdavis.com

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