How Will Thunderbolt Affect Enterprise Storage?

Last week, Intel and Apple dropped a bombshell on the consumer computer peripheral market. The new Thunderbolt port, a 10G bps interconnect found on Apple's latest MacBook Pro laptop computers, combines DisplayPort video and PCI Express and is opening a new world of expansion options. But how will this technology, formerly known as Light Peak, impact enterprise storage?

Essentially, Thunderbolt multiplexes two full-duplex PCI Express channels with DisplayPort video to expand the I/O capabilities of a computer. But Thunderbolt has some major points against it when it comes to enterprise storage use: It is fundamentally a personal computer interconnect, intended for docking stations, not data centers.

Although prototypes and future versions use compact fiber optic connectors (thus the "Light Peak" name), the production version of Thunderbolt uses electrical signals over a copper wire. That wire was a surprise: It rides along on Apple's Mini DisplayPort cabling spec, duplexing PCI Express data with digital video. Thunderbolt includes two full-duplex PCI Express channels, for a total of 40G bps of bi-directional throughput over a thin cable up to 3 meters in length.

Thunderbolt extends the host computer's PCI Express bus outside the physical chassis, allowing external devices to appear as though they are inside the case. Each peripheral will thus need its own Intel Thunderbolt de-multiplexer and PCI controller. Since Thunderbolt can flexibly manage the two included PCI Express channels, Intel promises high performance regardless of the other workloads sharing the connection.

In the future, we will likely see Thunderbolt hubs, optical repeaters and docking stations appear to increase the range and flexibility of this new I/O network.Two forthcoming storage peripherals, the Promise Pegasus RAID and LaCie Little Big Disk, exemplify what Thunderbolt storage will look like. Each includes a RAID controller chip alongside the hard disk drives or SSDs inside the case. This is a stark contrast to today's storage devices, which use a peripheral connect like Fibre Channel, SAS, FireWire or iSCSI.

This makes them more like direct-attached storage (DAS) than the networked storage devices we rely on in enterprise data centers. They cannot be shared natively among multiple computers, and are therefore not suitable for clustering or enterprise applications. Instead, they will offer massive performance for creative professional workstations and similar I/O-hungry users.

The fact that a single cable can carry both storage and video data at once is attractive to this market. Photographers and videographers, for example, are prime buyers of Apple's 17-inch MacBook Pro laptop. These professionals love the idea of connecting just power and video to transform their laptops into workstations when they return to the studio. The performance of Intel's new Sandy Bridge Core i7 CPU seals the deal for them.

The two protocols used by Thunderbolt--PCI Express and DisplayPort--are both absolutely required, at least for now. Intel's Thunderbolt Controller requires a DisplayPort signal along with four PCI Express lanes to function, something most rack-mount computers just don't have. This means that add-on cards are unlikely, and an Intel spokesman confirms they are not forthcoming.

This is not to say that Thunderbolt will never come to the server space. An inexpensive interconnect with two 10G bps full-duplex channels is certainly an attractive alternative to 6G bps SAS. And moving the RAID controller to the expansion shelf would allow far greater performance in the scale-up storage market.But Intel must first remove the DisplayPort video requirement. There is no reason to require it beyond personal computer compatibility, and MacBook Pro users are unlikely to plug into a rack-mount RAID enclosure. The video is multiplexed with the data signal, and the controller can fall back to video-only mode. Why not fall forward to PCI Express-only, as well?

The biggest stumbling block for Thunderbolt is not technological, however. It is the fact that Apple directed the creation of the technology and appears to have exclusive access to it until 2012. Apple is perhaps the least enterprise-friendly computer maker, and seems set on snubbing the corporate market.

Consider Apple's continuing exit from the enterprise space. The company unceremoniously dropped its Xserve RAID Fibre Channel storage system in 2009, and killed the rack-mount Xserve servers at the end of 2010. Now the word has come out that the server version of its next operating system, Mac OS X 10.7 "Lion," will be a mere feature pack for the desktop offering. Apple clearly wants no place in the data center.

Intel would likely love a market for its Thunderbolt chips besides the still fairly small world of Apple-loving creative professionals. But will Apple allow the use of its Mini DisplayPort connector without the video signal? Might we see a parallel technology using a different connector and, perhaps, an alternate name?

A more-likely future would be development of an open alternative for external PCI Express connectivity. The legions of chip makers left out in the cold by the Intel/Apple move likely have both the resources and desire to create such a protocol. Perhaps this will be Thunderbolt's real effect: spurring the creation of a new PCI Express-based interconnect for the data center.