Xserve: Apple's little big iron

If I'm not otherwise engaged next Thursday morning, I just might spend my economic stimulus check to enter the PC server business. I could go shopping for a wholesale 1U bare-bones rack server, with my primary criteria being that it boot DOS from a floppy and require you to take your server off-line to change basic system settings. I'll stuff that two-socket black box with RAM, CPUs, and disks; charge you for your choice of Windows or Linux; and unless you're buying these things by the gross, stick you with desktop-grade support. Since I had no involvement in your server's design and engineering, I'll rely on BIOS and driver updates from my volume motherboard supplier. I'll selectively pass these on to you, flagged with warnings about how they may render your system unusable if you misapply them, until my supplier stops issuing them. Don't worry, you'll have a solid year before that happens.

This would be a ridiculous way to open a review of Apple's latest Xserve if it didn't describe a sub-$5,000 PC server so well, as well as everything that Apple neglected to design into its eight-core, 1U Unix rack server. While Apple's latest Xserve uses the Intel Harpertown quad-core, Core 2 Xeon CPU, it is in all other regards the glorious antithesis of a PC server. With Xserve, Apple designed and engineered everything in-house, from the logic and firmware to the chassis and OS and admin tools. Support issues are not finger-pointed out to Microsoft, Novell, Red Hat, or GNU. Like your feature requests, your support tickets can land on the desks of the engineers who created what you're using. Xserve is built and supported to run not for one or two years, but three years, five years, and beyond. If you think I'm having you on, try to find a bargain Xserve on the refurbished market.

You expect the best of everything when you buy a proprietary big iron Unix server from IBM, HP, or Sun with a base of $20,000. If you want big iron Unix server features from a 1U x86 rack server with an entry price around $3,000, or $5,000 with eight 64-bit processor cores, you take your business to Apple. And unlike the big iron Unix servers, Xserve can consolidate your Windows, Linux, and even OS X servers through Parallels or VMware virtualization. Xserve extends its standard benefits of online and lights-out remote GUI (or command line) management and the rich services of the bundled OS X Leopard Server (true, certified Unix) to all applications and OSes the Xserve hosts. (See "Leopard Server: The people's Unix.")

No forks in the road
Consistency and continuity are hallmarks of Apple designs. The eight-core Harpertown Xserve is, at heart, the quad-core Xeon Xserve system that I detail in my review of the first Intel-based Xserve (see "Apple Xserve: The final review"). The Harpertown model is significantly enhanced but not reworked. If you have a four-core Xserve, you don't need to replace it to stay current with the vendor's latest technology. Apple's free, automatic software and firmware updates make four- and eight-core Xeon Xserves functionally identical. For that matter, dual- and quad-core (two-socket) PowerPC G4 and G5 Xserves run the same Leopard Server OS and are managed the same way, albeit without Xeon Xserve's lights-out and x86 guest OS capability.

As Intel worked it, Apple could have made the transition from a four-core server (two cores by two sockets) to eight cores by doing nothing but a chip swap, but Apple didn't settle for a mere processor upgrade. Apple's original Intel Xserve design was built to embrace evolution while keeping the price either flat or on a downward curve relative to prior generations. Brilliant reuse of design elements results in lower design and manufacturing costs for each generation of Xserve, but instead of taking the lower cost as a windfall, Apple shares it with buyers in the form of upgraded standard features.

What's new
While fully compatible with its four-core Xeon predecessor, the new Xserve is new in some key ways that set markedly higher standards for performance and flexibility. Intel's Harpertown Xeon CPUs bring a cooler (meaning less hot) 45-nanometer manufacturing process to the mix, as well as a whopping 12MB of Level 2 cache per socket. The new Xserve's PCI-Express 2.0 bus welcomes the latest high-speed network and host bus adapters, but the expansion bus maintains compatibility with PCI-X cards that have been in the Xserve family since PowerPC.

Another throughput-boosting enhancement is the shift from 667MHz FBDIMM DDR2 RAM to 800MHz modules. Paired with Harpertown's per-socket L2 cache of 12MB, higher-memory bandwidth opens up the total system headroom needed to make worthwhile use of eight processor cores. Most commercial software is more throughput-bound than CPU-bound. On Intel architecture machines, RAM, bus, and cache are where you really feel the difference. The new Xserve delivers on all three.

Apple has added an onboard AMD/ATI 3-D GPU (graphics processing unit) with 64MB of video RAM. This allows the frequent use of Xserve's console, including Apple's demanding Aqua GUI, without inflicting the drag on the CPUs and main memory that Intel's integrated graphics does. For creative and scientific applications where the onboard GPU isn't enough, Xserve can be purchased with a PCI-Express graphics adapter. Though a server acting as a workstation is not a corporate usage scenario, where batched server workloads are the norm, there's no reason to let Xserve's console lay dormant between runs. Xserve's standard SuperDrive dual-layer DVD burner reflects that Xserve is flexible enough to be harnessed by a user.

In a small-business setting, Xserve's improved ability to handle interactive tasks can be a real boon. While Xserve is too loud to make a good office mate, placing it in a noise-isolated chassis (like GizMac's XRackPro) or using affordable video and USB extension cables may obviate the need for a desktop. OS X Leopard Server runs the same applications as the OS X Leopard client operating system shipped with Mac notebooks and the Mac Pro desktop/workstation. Unorthodox? Certainly, but giving a server whose utilization floats around 30 percent the pleasure of serving a user seems fit for the present economy. Apple further enhanced Xserve's local usability by placing a USB port on the front panel.

Server-based storage is one of Xserve's strong points, and Apple has taken it to an extreme. As before, Xserve has three bays for removable drives, and each bay accommodates not only the Serial ATA drives common to entry PC servers, but also SAS (serial attached SCSI) drives that spin at up to 15,000 rpm. You can configure your Xserve with any mix of SATA and SAS drives, setting your own balance of speed and capacity. On the subject of capacity, new 1TB Apple Drive Modules, which are compatible with the preceding Xeon Xserve as well, bring the total server-local storage capacity to 3TB.

At around the same time that Apple shipped the new Harpertown server, it delivered a hardware RAID card that is installable in any Xeon Xserve. This $999 option is invisible once installed; it replaces the backplane into which the SATA and SAS drive bays plug, and therefore does not consume a precious expansion slot.

Hardware RAID changes the character of Xserve, carrying it into an entirely new class of server. The RAID add-in is the real deal, with battery-backed write cache, transparent and autonomous building and rebuilding of parity and mirrored volumes, and boot capability even when a drive in a parity set fails.

I consider the RAID option non-optional for commercial use. Its only downside in my testing was frequent complaining to the console whenever the battery's charge wasn't sufficient to hold data for 72 hours without power. It says something about the RAID controller that it considers 72 hours a low-water mark for cache retention after the plug is pulled, but I can do without the notices.

Like all Xserves, the Harpertown model is self-aware to a fault (pun intended). It's loaded with thermal, fan rotation, current, and voltage sensors. Xserve reacts to trouble on its own, and it shares the statistics from these sensors with you in detail. That, in my opinion, is one of Xserve's best features. But sensor and system configuration data are also available out of band during operation and when the server is not running. Every Xserve ships with a baseboard management controller (BMC) of Apple's design that conforms to the IPMI 2.0 standard. Access to the BMC is protected by redundancy, with both of Xserve's onboard gigabit Ethernet ports wired into it. Apple's GUI-based Server Monitor taps the BMC from any Mac through IPMI, and from any POSIX-based system using an open source command line tool.

Virtually ideal
OS X Leopard supported hypervisor-based virtualization before Windows Server did. Despite the name, Parallels Desktop runs multiple instances of any mix of 32-bit x86 OSes, including most Windows Server versions, along with commercial and free Linux distributions, BSD variants, Solaris, and more esoteric choices. VMware Fusion does the same, with support for 64-bit operating systems as well. Both Parallels and VMware are working on server-specific editions of their Mac products; Parallels Server for Mac is in its fourth round of beta testing now, and has just taken on the ability to host OS X Leopard Server as a virtualized guest. Only Leopard Server can host Leopard Server, but this capability will soon make Xserve the only box that can run all commercial x86 operating systems in virtualization.

Stripped or loaded?
The least you can pay for Xserve is $2,999 for a four-core machine with 2GB of RAM. This is capable enough for small businesses, but the empty CPU socket can't officially be filled post-purchase. Xserve's sweet spot for pricing is $3,999, which buys you an eight-core machine with 2.8GHz CPUs and 4GB of RAM. Incremental improvements to the base config start to get pricey, which is a reflection of component costs rather than Apple margineering. For example, Xserve with 8GB of RAM and two 3.0GHz quad-core CPUs prices out at $5,799. You know that RAM and hard drives will get less expensive over time, and you can upgrade both of these later. As for paying extra for higher CPU clock speed, you would need a stopwatch to measure any difference in application performance from that extra 200MHz per CPU.

The pleasant surprise is the price of a fully loaded Xserve. Harpertown Xserve with eight 3GHz cores, 3TB of internal hardware RAID storage, and 32GB of RAM cruises in at under $10,000. There are 1U x86 rack servers with smaller price tags, to be sure, but none that can be taken so far in one chassis as Xserve for the money, and no PC server carries pervasive big iron design to the mainstream as Xserve does.

Additional resources
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• Review: Mac OS X Leopard: A perfect 10
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• A developer's-eye view of Leopard, part I
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• A developer's-eye view of Leopard, part III
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• A developer's-eye view of Leopard, part IV
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• Analysis: Leopard's Unix tricks
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• Hands on: How to make the (new) iPhone work at work
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• Tom Yager: Enterprise Mac