4Gb/s: coming soon to a SAN near you

Computer Technology Review,  Dec, 2004  by Lovest Watson

• E-mail
• Print
• Link

It's not often that storage customers get "something for nothing." But that is what will happen within the next year for customers who install 4 Gb/s Fibre Channel SAN components. At little to no additional cost, vendors will deliver SAN components with twice the speed of existing SAN components, all with guaranteed interoperability with earlier generation 2 Gb/s products.

Driven by the ever-increasing demand for storage from corporate applications, storage vendors are today preparing SAN infrastructure components that will double the speed of today's 2 Gb/s storage switches and the host bus adapters (HBAs). Customers who invest in 4 Gb/s components in 2005, even if they currently lack the demand to fully utilize this increased bandwidth, will be ideally situated to save through increased application performance, faster backups and recovery from hardware failures, and avoidance of future SAN infrastructure upgrades.

Why 4Gb/s?

Whether because of e-commerce, regulatory requirements or everyday applications such as e-mail, enterprises need faster and faster access to more and more data every day. Throughout their IT infrastructures, the speed and data handling capacity of microprocessors, disk drives, data networks and databases are all continually increasing as well. To keep up, every part of the organization's storage infrastructure must grow in capacity as well.

The most commonly used storage protocol for medium and large companies is Fibre Channel, which is used to link servers to storage switches, storage switches to disk arrays, and disk arrays to each other within Storage Area Networks (SANs.) Most FC SANs currently run at 1 or 2 Gb/s, a data transfer speed which is adequate for many current storage needs. However, the upcoming 4 Gb/s products will address a number of current, or upcoming, storage challenges. They include:

The emergence of servers utilizing the new PCI Express bus. Compared to the current PCI-X bus, PCI Express will more than double the rate at which data can be transferred between server memory and peripherals such as HBAs. PCI Express is highly scalable, with speeds expected to increase from the initial 2.5Gb/s to as much as 80Gb/s, depending on the implementation. PCI Express offers other improvements such as enhanced data integrity, as well as improved error reporting and handling. Its adoption is expected to be sped by the fact that, like 4 Gb/s Fibre Channel, PCI Express will be software compatible with earlier generations of technology (the PCI-X and PCI buses.) Investing in the new generation of 4 Gb/s SAN components in 2005 ensures these PCI Express servers will not face a bandwidth bottleneck as they communicate with storage switches and SANs.

The need to reduce the time required to back up large application databases to tape. Tape continues to be the preferred medium for long-term, off-site archival storage of data. New regulations, along with the need for such archived data for disaster recovery, are constantly increasing the amount of data organizations must archive. Yet transferring such data from a FC SAN to tape often requires taking the source application off-line, which interrupts users' work and overall efficiency. By allowing data to be shipped from the SAN to the backup devices more quickly, upgrading to 4 Gb/s FC can shorten this "backup window" and provide regulatory compliance and disaster recovery without interrupting everyday business processes.

Growing needs for server consolidation. By virtualizing dozens or even hundreds of servers on each port on a FC switch, customers can make more efficient use of their server resources while reducing the number of storage switches they must buy and maintain. Each storage switch must, however, be able to handle the increased amount of data moving to and from the consolidated servers. Purchasing 4 Gb/s FC components now gives customers the flexibility to implement very large-scale server consolidation as their needs and advancements in virtualization technology dictate.

Scalability for demanding applications. Applications such as on-line transaction processing and those involving digital media (such as video on demand) have the potential to strain even today's most robust SAN infrastructures. For example, a transactional system generating 50,000 I/O (input/output) operations per second, with each operation involving only 4 Kbytes of data, can saturate a 2 Gb/s FC link. Purchasing 4 Gb/s SAN components can, at no additional cost beyond that of 2 Gb/s products, accommodate such I/O streams without slowing the applications on which they depend.

The need to reduce RAID rebuild times. Organizations deploy RAID (redundant array of independent disk) subsystems so that in the event one drive fails the data on it can be recreated from parity data stored on the other disks in the array. The speed with which the data can be recreated, of course, depends in part on the speed with which the parity data can be read from the other disks. Purchasing 4 Gb/s FC components assures customers that as the capacity of the drives within their RAID arrays increases, the time required to rebuild RAID drives (and thus to assure business continuity after a hardware failure) will remain within acceptable limits.