VMware delivers a datacenter in a box

VMware, now owned by EMC, created its ESX Server virtualization product for businesses that need truly enterprise-class virtualization. ESX Server 2.1.1 implements the consolidation, dynamic provisioning, resource pooling, and all-bases-covered availability assurance of expensive system and storage hardware. But ESX Server does it with ordinary servers, modular SANs, and vanilla operating systems.

I started testing with a pair of dual-processor rack servers -- one Opteron and one pre-Nocona Xeon -- but then moved to a single Opteron DP server and a pair of stand-alone Athlon FX (single-processor desktop Opteron) systems to get a better feel for ESX Server’s approach to distributed management.

My expectation going into this review was that ESX Server would perform similar to VMware’s lower-end GSX Server  product, just scaled for higher-volume environments. It will serve that purpose, but limiting it to the typical consolidation/isolation role strikes me as a poor investment. What’s revolutionary about this product is that it creates a fabric of physical servers, VMs, and networked storage volumes that connect in any-to-any, many-to-many fashion.

VMware strongly advised me to use a heterogeneous SAN for my tests. I put an Apple/LSI Logic dual-port Fibre Channel adapter in each server and used an Emulex 355 storage switch to link the servers to a pair of Apple Xserve RAID disk arrays. In practice, setting up the SAN took longer than installing ESX Server and the guest operating systems, but I can’t overstate ESX Server’s brilliant use of networked storage. It implements its own SAN file system, replete with leading-edge features such as read/write volume sharing, file-level locking, and multipathing for transparent fail-over and volume spanning. ESX Server’s virtualization layer delivers all this SAN goodness even to operating systems that don’t have Fibre Channel drivers; to each guest OS the SAN looks like a simple SCSI adapter.

ESX Server handles the LAN transparently, too. When it routes around network traffic jams and card failures or relocates VMs from place to place, the guest OS is clueless. It sees the same set of network cards and the same fixed IP addresses.

VMware licenses ESX Server on a per-CPU basis. Its host core is a custom Linux kernel with a limited set of bulletproof device drivers, for reasons of stability. The hardware compatibility list for ESX Server is thus very short, but all my dual-processor Opteron and Xeon systems proved compatible without alteration.

Although they are not a specific focus of this review, I used three optional VMware products in my testing: VirtualCenter, a scalable provisioning solution; Virtual SMP, which creates dual-processor VMs (a significant advance); and VMotion, which allows you to move a running VM from one physical location to another without interrupting its execution.