Issues To Watch For With Blade ServersBlades Offer Advantages In Size & Convenience But Present Some Hidden Headaches
Written By Kurt Marco - Processor-Vol. 26 Issue 012
Since their introduction more than six years ago, blade servers have evolved from a clever, high-density packaging solution to an integrated platform incorporating server, network, and storage components. The increased capabilities and convenience of the latest blade products have resulted in revenue for the category soaring more than 40% this year, with the total market estimated by IDC to have passed $1 billion this past quarter. Despite their recent popularity, blades still make up less than 10% of the overall market; however, as IT departments consider spending priorities for the next year, many are likely wondering whether blades should be added to their infrastructure mix. While blades offer a number of advantages over conventional rackmount servers, IT experts don't give them an unqualified recommendation because blades can pose nasty surprises for users who don't do their homework.
Blade Strengths & Challanges
The principle advantage of blade servers, and the feature universally touted by manufacturers, is the increased density and ease with which additional servers can be deployed. Gartner analyst John Enck notes several other benefits, such as simplified hardware maintenance via the ability to quickly swap failed components and reduced cable clutter from an integrated chassis. He also notes that blade management software enables new servers to be quickly provisioned using simple scripts or a few mouse clicks.
Enck says that each product's proprietary design--there isn't a standard backplane interface that allows mixing and matching of blade components from different vendors--is the biggest disadvantage. This inevitably leads to vendor lock-in. He finds that once customers have committed to a blade solution, they must load the entire chassis with a single vendor's products, meaning that a blade usually entails establishing a strategic vendor relationship. Enck notes that limited configuration options that hinder flexibility, while somewhat mitigated with recent designs, is another challenge with blades.
The rapid rate of technological change in the blade market is also cause for concern. "The history of blades shows that the technology has undergone a revolution," Enck notes. "This revolution will continue, with vendors investing in new features and technologies, which leads to faster obsolescence than found in the wider server market."
Blade "Gotchas" To Watch For
Blade buyers also need to be cognizant of a number of more subtle issues concerning power, cooling, and interoperability. William Terrill, associate senior research analyst with Info-Tech Research Group, has identified four blade server "gotchas" that may trip up unsuspecting users. The increased density of blade servers can lead to problems in deployments that don't adequately plan for heat removal. Terrill says that although "the amount of heat generated by blade servers is less than that created by equivalent rackmount servers, the blade chassis concentrates that energy, creating a higher density of heat within a small physical space. As a result, airflow created by blade server fans has a higher velocity than that from single rackmount servers." Consequently, installing blades in smaller computer rooms with inadequate ventilation will cause hot spots. Furthermore, he notes that many standard blade configurations may not include enough hot-swappable fans to adequately cool a fully loaded chassis, thus buyers should consider adding optional fans.
Similarly, Terrill finds that inadequate power-supply capacity has plagued some blade configurations. Although current chassis designs have mitigated or eliminated the most catastrophic power issues, he says, "as new, more power-hungry (multisocket, multicore high-performance) processors are introduced, it is possible that the power demand may, once again, outstrip the capacity of the power supplies." Buyers should also investigate whether a fully populated chassis will continue to operate properly in the event of a power supply failure. Terrill notes that most chassis support four supplies and that new designs typically throttle back CPU performance in the event of a supply failure, but he notes that blade users "may not have as much redundancy in the power supply as you think."
Blades are popular as the foundation for virtualization, with a typical scenario using a SAN to consolidate storage for a blade server cluster. Terrill says, "In order to take maximum advantage of both the SAN and virtualization, the individual processor blades should have no onboard hard disk" and instead boot the OS directly from the network. Unfortunately, he has found that while all vendors support booting from Fibre Channel SANs, booting from iSCSI can be problematic. Terrill says blade buyers with iSCSI arrays should carefully study the spec sheets, advising that unless the vendor explicitly states support for iSCSI boot-from-network for a particular OS, it probably won't work. Gartner's Enck concurs but cautions that buyers may still run into interoperability issues when trying to mix blades and SAN arrays from different vendors. He notes that blade vendors typically only certify on their own storage devices, so those building heterogeneous solutions may run into finger-pointing between vendors if problems arise.
Enck sums it up saying that "blade solutions do not always connect well to established SAN and network environments. The ecosystem to ensure cross-vendor support for storage and networking technology at the interconnect and manageability levels is not well-developed."
Another area in which blade servers can introduce unintended complexity to an IT environment is in management of integrated I/O modules, particularly LAN switches. According to Terrill, problems can arise when using Layer 3 switch modules rather than a simple pass-through cross-connect that routes to an external switch. "Configuration and management of the module may require different tools than the rest of the enterprise networking components," he says. Organizations already standardized on Cisco (www.Cisco.com) gear may feel compelled to use Cisco modules because they have products for all major chassis. Terrill cautions that this usually involves a price/performance trade-off because Cisco is usually more expensive.
A Note Of Caution
Blade servers offer real benefits in density, deployment convenience, and power consumption, and experts say they are worth considering when deploying eight or more servers. Yet Terrill notes, "There are some areas that continue to be potential issues with blade server installations, all of which can be dealt with" through careful consideration of the potential pitfalls.
AVTECH Software, Inc.