Coraid Blog

Affordability and Performance - The Ultimate Challenge of SAN Technology

Once the Gigabit Ethernet standard was announced in the late 1990's, it became clear to the CORAID co-founder, who is also the inventor of the Cisco PIX firewall, a new alternative may exist for network storage without the high costs and limiting factors of Fibre Channel and iSCSI.  A goal of making high performance network storage that is also affordable became a reality with the open network protocol designated AoE, short for ATA-over-Ethernet. AoE was pioneered by CORAID and is supported by Linux and is available as part of all major Linux distributions. CORAID's AoE is a competing technology to Fibre Channel and iSCSI. AoE is freely available to anyone. CORAID EtherDrive storage appliances, all based on AoE, are available at a fraction of the cost of comparable storage products and solutions, thus enabling VMware ESX customers a needed option for network storage which is high performance and very affordable.

When the decision was made to use Ethernet to enable network storage, it quickly became apparent that the true speeds of Ethernet had to be fully realized and could not be by using TCP/IP. In networking there are several layers to consider when designing a network protocol, starting with the physical layer, the fastest, all the way to the software driver or application layer.  These layers too often depend on generic handling of networking details at lower layers causing too much overhead and processing, thus resulting in much slower speeds and performance as a result. Unfortunately TCP/IP fits this slow case when trying to enjoy the speeds available with Gigabit Ethernet. Therefore the design goal became clear; develop the network protocol as close to the hardware layer as possible, yet have it be manageable enough so as not to be tied to one piece of Ethernet hardware.  Ethernet datagrams fit this design goal and became the cornerstone of the yet unnamed protocol. As it happens, using only datagrams for a protocol, translates into enormous scaling and performance benefits when the protocol is developed in a pure, clean manner.

Keeping in mind the design goal of maximum Ethernet speed, it became imperative to have the proper, efficient message structure and commands to make Ethernet based network storage a reality. Embedding ATA commands into the Ethernet datagrams fit this design goal exceedingly well. The ATA commands completed the protocol, aptly named "ATA-over-Ethernet", or AoE. It is important to note that because AoE is a true protocol, it does not matter what type of hard drive is used when implementing the protocol and corresponding driver. CORAID develops its EtherDrive storage appliances for the most affordable and reliable hard drives on the market to benefit users controlling costs while providing ease of storage growth and management.

For information on CORAID EtherDrive SAN visit www.coraid.com

Virtualization - The Promise (Part II)

Access to network storage, the myriad of network connections and paths used to get to the data, grows in a non-linear manner with high demand and full utilization of the network. Hence, network storage is really a networking challenge, not a storage challenge. Fibre Channel and iSCSI were designed by storage experts.  ATA-over-Ethernet (AoE) was designed by network protocol experts.
In the early days of Ethernet, network speeds were sufficient for basic communication between computers, but certainly not for network storage. The original Ethernet standard(10Mbit/s) evolved into Fast Ethernet(100Mbit/s) and next into Gigabit Ethernet(1Gbit/s), with an even more recent 10 Gigabit Ethernet(10Gbit/s). Once Gigabit Ethernet arrived in the market it had widespread adoption, therefore produced in mass quantities making the NIC's very affordable for everyone as commodity products. Finally Ethernet had the speed at 1Gbit/s that could theoretically match the media transfer rate of hard drives at 1Gbit/s or higher. The challenge now became how to fully realize the performance speeds of Ethernet and to make the market aware of how today's Ethernet can readily handle the demanding networking load required by network storage.

The inventor of the Cisco PIX firewall and CORAID co-founder wrestled with the challenge to fully realize the performance capabilities of Ethernet for network storage by designing an open network protocol called ATA-over-Ethernet (AoE). The significance of AoE is its very lightweight footprint, with a specification of only 11 pages.  AoE is the enabling framework that allows EtherDrive SAN to be high performance and affordable. Because AoE only relies on Ethernet, all of the components to create and manage an Ethernet based network are available as very affordable, commodity networking hardware. Taking this approach has allowed CORAID to create high performance storage appliances by assembling commodity technologies, thus keeping cost per GB of storage at $0.50, a very small fraction of the cost of other storage hardware in the market. VMware ESX users now have the much needed and unheard of combination of "High Performance and Affordability" for their network storage.

The robust and flexible nature of AoE has allowed CORAID to develop EtherDrive SAN storage with an almost unlimited amount of expansion. Each CORAID EtherDrive storage appliance is deemed a "shelf". AoE allows addressing, or access, to 65k of these AoE shelves. Each shelf in turn can host 255 targets. Each target supports 48-bit logical block addressing, or 144 Petabytes. Currently, available drive capacity and hardware limitations only allow for 10's of Terabytes per shelf. With over 16.7 Million (65k Shelves * 255 targets per shelf) targets available on a single network, each with a theoretical capacity of up to 144 Petabytes, it becomes clear why CORAID's almost unlimited expansion capabilities become critical to storage growth.

Just as important, if not more important than storage growth and capacity, is access to network storage. Without scalable network access, network storage quickly becomes a bottleneck for the entire system. For VMware ESX, CORAID helps solve this dilemma by simply adding one or more 2-gigabit (dual 1-Gig) EtherDrive HBA to get more bandwidth and leverage available network capacity. Fibre Channel and iSCSI cannot scale in this manner and are therefore doomed to become network storage bottlenecks because they are not robust enough to scale to existing network capacity cost effectively.  By today’s standards, the ultimate performance is achieved by using one or more 20-gigabit (dual 10-Gig) EtherDrive HBA. This enables VMware ESX to fully leverage high performance network storage at maximum network capacity with the benefit of the most affordable price.

For information on CORAID EtherDrive SAN visit www.coraid.com

Virtualization - The Promise (Part I)

CORAID is committed to providing very high performance at the most affordable price. The EtherDrive Host Bus Adapter is a doorway for many users to enjoy the benefits of a storage area network affordably for the first time in conjunction with VMware's ESX virtual environment capabilities. The EtherDrive HBA allows ESX users to use EtherDrive SAN storage and is very inexpensive. Network storage can now be virtually assigned and managed for maximum utilization with the combined power of VMware ESX and CORAID's EtherDrive SAN.

Disk capacity used to be very limited, therefore allowing all disks to remain part of the server. Once hard drive capacity and speed increased there was no longer room for hard drives on a single server. Additionally, more applications and users began to require more and more access to the same data, so the data had to become available in a centralized, more easily managed method. Speed and the ability to scale capacity became more and more important as the need and availability of centralized data became mission critical.

At the time, the available networking technologies, including Ethernet, were not capable of the high throughput required to make network storage a reality. The problem was viewed as more of a storage problem, however, and not a network dilemma. Fibre Channel, originally designed for simplifying connections and increasing distances, was co-opted as the solution to provide the speed and reliability required to make network storage a reality. Fibre Channel evolved into a rebuild of all network layers from the ground up. This makes Fibre Channel hardware more complex and proprietary. This combined with the fact only relatively small volumes of Fibre Channel hardware are sold, makes Fibre Channel very expensive to own and manage with no hope of it becoming affordable at commodity prices.
Another unfortunate drawback of Fibre Channel (iSCSI too) is that it is connection based, meaning two well defined end points must be configured and managed tightly. Although connection based protocols are secure, reliable and can have decent speed, they do not really allow for leveraging the existing network infrastructure.  With ATA-over-Ethernet (AoE), increasing the overall speed and throughput is accomplished simply by adding another host bus adapter to get more overall speed and throughput. Without increased (scaled) network capacity it is impossible to grow storage capacity seamlessly and without exorbitant costs. Another very real issue is how different applications, users and systems need access to network storage in demanding and often times unseen ways. Storage needs grow in a linear fashion with capacity planning being straight forward. Access to network storage, the myriad of network connections and paths used to get to the data, grows in a non-linear manner with high demand and full utilization of the network. Hence, network storage is really a networking challenge, not a storage challenge.

For information on CORAID EtherDrive SAN visit www.coraid.com