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On the surface, Apple's Snow Leopard Server feels like a $499 maintenance release, but underneath, there's much more -- improved performance, more polish and new apps focused on collaboration and content sharing.

Apple's new installation routine for Snow Leopard (Mac OS X 10.6) improves upon Leopard's (Mac OS X 10.5) Easy and Advanced installation choices. With Snow Leopard, choices are clearer, and fresh installations usually make prudent default choices.

We easily installed the new Address Book Server, updated Mail, a new Mobile Access Server, WiKi service, an iCal(endaring) server, iChat server, filesharing and backup server (an update to Apple's Time Machine software). After the applications are installed, we had to configure service, users, groups, and the like on a fresh installation, but an upgrade from Leopard requires little settings work.

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We were happy to find tough password policies available for user accounts, but not so pleased to find that the administrator password could be very weak by default.

The Address Book server app, which allows multiple computers to share contacts, is new. It joins with directory services (Apple's Open Directory, and Microsoft's Active Directory via open source Samba) rather than be an extension of Open Directory. Address Book is compatible with Zimbra open source email, and is modeled after WebDAV, as an XML-based extension of the venerable vCard. It stores vCards outside of the directory service.

The Address Book server isn't backwards compatible with Leopard, because the protocol it's based on, CardDAV, didn't exist when Leopard was developed. Users can merge their contacts into the server easily enough -- if they're Snow Leopard users.

Apple adds a new service to Snow Leopard, the Mobile Access server. A "VPN-less" authenticated/encrypted entry method that's designed to sync iPhones, Mac clients, to their address books, mail, and other internal resources. Advanced connections can be completed through Apple's L2TP/IPSec-based (or old-fashioned PPTP) VPN connectivity.

Similarly, another new app, the iPhone Configuration utility, can provision and synchronize a fleet of iPhones. As we don't use iPhones, we were unable to test the Mobile Access Server's iPhone accessibility and the applications sadly don't work with other mobile operating systems, although third parties may be able to offer this for other phones in the future. Nonetheless, it's the first time any of the operating system vendors have paid much attention to fleet mobile/cell provisioning, aside from RIM's primitive BlackBerry message servers.

Podcast Producer 2 is an updated server app that benefits from Apple's Xgrid compute clustering application. Xgrid processes workflows (often things such as media encoding) either on the host server or on other Apple MacOS machines.

In MacOS 10.5, Xgrid is difficult to make workable on distributed Mac (server or client) hardware unless one has advanced integration skills -- and is willing to troubleshoot error logs until the application works. On Leopard, it took us nearly a day to work through and troubleshoot all of the elements of the distributed processing of Podcast Producer and Xgrid.

Snow Leopard, by contrast, takes Podcast Producer 2 with updated Xgrid2 and installs a workable version that's capable of distributed podcast encoding in about five minutes, doing all of the homework and connectivity bits itself, painlessly.

A similar example of better "fit and finish" is Podcast Composer, which allows easy creation of Podcast Producer2 workflows, compared with the MacOS 10.5 version's way of creating workflows by hand.

It's important to note that Snow Leopard does not run on older Apple servers running G4/G5 (IBM PowerPC) processors. In a sense this is a plus, because once installed onto newer Intel-based Apple hardware, the Snow Leopard OS footprint actually shrinks by several gigabytes, since PowerPC code is deleted.

With the dumping of PowerPC server support code, Apple has made several fundamental changes to MacOS in terms of memory management models and in capacity performance for applications. Thus, performance improves.

Like all Apple operating systems, Snow Leopard is captive to Apple's hardware, which is currently limited to 1U-sized Apple Xservers (and hefty MacPro desktops). This means there are no blade variations, no 4U/16-core muscle machines, like HP's DL580/585 G5 servers. Nonetheless, Apple's Snow Leopard performed faster than its predecessor, Leopard 10.5.8, in our testing, due to some of these operating systems enhancements.

Improved administration

Administration is somewhat improved with Snow Leopard. Apple's Server Preferences administrative application in Leopard was available only if Advanced wasn't chosen; we've not used them subsequently because Server Preference choices had no depth and were superficial.

In Snow Leopard, simple basic administrative choices can be performed in Server Preferences, but aren't likely to be used by very many administrators. We wonder why it's still around, save that it's a safe choice for small, civilian-run networks. Server Admin still does most of the work of managing the MacOS server system and its services.

Performance inside performance

Apple attempts to achieve scale for its apps via something called "Grand Central Dispatch" (GCD). The idea behind GCD is to more efficiently use multicore processor resources by aiding parallelism in applications across processors.

The technical explanation of GCD is simple, and programs don't necessarily have to be specifically GCD-enabled to benefit from GCD parallelism, although it helps. Sitting in userspace, the GCD is designed to allow Apple's Snow Leopard to be more efficient in its use of memory and resources for programming needs.

It does this by allowing apps that can sense the GCD to spawn threads that are very small, compared with other operating system (especially Linux) schemes. Apps that simply use GCD-enabled services, like Apache or file services, also get a boost from more efficient MacOS, GCD-enabled infrastructure. Apple released GCD code to open source developer trees under the Apache and MIT licenses after MacOS 10.6/Snow Leopard was released.

Perhaps as a consequence of the now-removed PowerPC support, MacOS 10.6 can take advantage of differing memory models (64-bit) which we believe helped in our SPECjbb2005 test. SPEC's JBB test is an emulation of a business application using Java that delivers a result in Business Operations per Second (BOP).

In an apples-to-apples comparison, Snow Leopard is 4% faster than Leopard. Add in the ability to use large memory pages, and the figure is 21% more BOPs. When we lowered the available total memory but increased the number of Java Virtual Machines servicing SPECjbb2005, the large memory size helped but it didn't appear as though the new GCD helped performance in this benchmark.

Henderson is principal researcher and Allen is a researcher for ExtremeLabs in Indianapolis. They can be reached at thenderson@extremelabs.com.

Henderson is also a member of the Network World Lab Alliance, a cooperative of the premier reviewers in the network industry each bringing to bear years of practical experience on every review. For more Lab Alliance information, including what it takes to become a member, go to www.networkworld.com/alliance.

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