Comparing Linux and Microsoft Windows for Enterprise Usage
Active Directory is the heart of Microsoft networking. It is a powerful tool that has a solid reputation for providing reliable directory services. Chances are, unless you are already a *nix shop, you're probably using it right now. AD has dominated the landscape for so long that many people forget its roots. In the strictest sense, AD is an LDAP-based server that uses Kerberos for authentication and DNS for name resolution. The reason for its dominance is twofold: its flagship mail product (Exchange) requires it, and every Microsoft desktop and server OS shipped has a built-in AD client. Directory services existed before AD, and other alternatives are available (even non-Linux ones) that provide similar services.
One of the better alternatives is eDirectory from Novell (Figure 8). eDirectory has its roots in Novell Directory Services (NDS), the highly popular directory service that dominated the enterprise in the 1990s. Although Novell has lost considerable market share to AD in the last decade, it has continually improved its directory products. eDirectory is scalable, supports multimaster replication and is OS-agnostic, which means it can easily be deployed to almost any environment (including Windows). For Linux systems, eDirectory can run on either SUSE or Red Hat Enterprise servers. eDirectory can be managed by using ConsoleOne (Figure 8) or the newer, sexier iManager Web management package (Figures 9 and 10) that uses role-based assignment of privileges. This is similar to AD; however, the level of granularity over directory permissions found in iManager is far greater. As a side note, Novell currently has a standing relationship with Microsoft that each will support the other's products. This could be a benefit when campaigning for a bigger Linux presence in a Microsoft-centric enterprise.
Virtualization may be the hottest topic in the industry at the moment. It seems like “virtual” is the buzzword of every other Webinar out there. I won't spend time explaining the value of virtualization, save that server consolidation and desktop/application virtualization seem to be the biggest reasons so many people are interested in it. Microsoft made a major move into the virtualization arena with its release of Hyper-V. Unlike Microsoft's earlier product, Virtual Server, Hyper-V sports a fully virtualized hypervisor that removes the need for running a virtual server on top of a “fat host”. Hypervisors allow guests to access underlying hardware directly, and because there is very little overhead, performance is dramatically improved. Hyper-V has received a number of improvements with the release of Server 2008 R2. It now has more enterprise-grade capabilities for management and high availability, and most notably, support for live migrations. It can be managed with the Hyper-V Manager Console, an enterprise-grade tool for creating and managing Hyper-V hosts and guests.
There are Linux-based options for virtualization as well. For the longest time, Xen was the darling of the Linux virtualization movement. Following the acquisition of Xen by Citrix, many vendors have begun making the switch to using the Kernel-based Virtual Machine (KVM) module as their primary virtualization platform. KVM is a hypervisor module that can run in a kernel of 2.6.20 or higher, but it does require a compatible vm-enabled processor. Red Hat, formerly a huge supporter of Xen prior to its acquisition, has tied its wagon to KVM. In fact, Red Hat is releasing its KVM-based Red Hat Enterprise Virtualization (RHEV) product as a direct competitor to Hyper-V, VMware and Xen. RHEV is composed of a minimalist RHEL KVM-enabled installation, tweaked as a host system for virtualization. Unlike most virtualization products on the market, RHEV is rolling out a competitive subscription-based pricing model that includes both the hypervisor and manager software in the same license (often sold separately). It also touts advanced virtualization features, such as live migration and automatic server failover. I really wanted to test-drive RHEV for this article, but I was unable to obtain a trial version of the product. Regardless, KVM runs near flawlessly in most distributions. For demonstration purposes, I deployed KVM on Ubuntu, which provides a Just enough OS (JeOS, pronounced “juice”) image configured specifically for virtual appliances. KVM hosts can be managed using the GUI-based virt-manager package (Figure 11) or other command-line tools.