Edges Extending Data Center SAN Advantages to the Workgroups Kompetenz in SCSI, GmbH Fibre & Fiber
Extending Data Center SAN Advantages to the Workgroups Today's business environment demands a storage area network (SAN) to manage the growth, availability, and manageability of a company's most valuable resource - data. With data representing the heart and soul of every business, IT professionals can not afford to choose the wrong SAN infrastructure components. Just as low-end fibre channel switches and hubs are not robust enough for a data center environment, high-end directors and departmental switches are not cost-effective for connecting low-end edge devices such as workgroup servers and storage devices. Edge switches provide cost-effective connectivity to the data centre for workgroup devices while also providing the manageability, reliability, and serviceability required in today's mission-critical SANs. Today's SAN must be built with right-sized building blocks from the Enterprise to the Edge. Introduction Storage Area Networks (SANs) are becoming the mainstream solution for organizing and managing today's ever-increasing volumes of storage. SANs enable IT managers to recognize, plan, and manage storage as an independent resource - free of the restrictions and logistical complications of directly attached storage. The advantages of SANs are widely recognized. SANs remove the distance and speed limitations of SCSI connections, provide higher availability, are easily scaled without disrupting operations, offer increased data security, and better protect data through faster and more reliable backups. SANs encourage an information-centric view of the IT organization vs. the traditional processor-centric view. With an information-centric view, data is recognized as the primary IT asset, and therefore, processors and networks are implemented in support of the data. Finally, managing a SAN is notably less costly than managing multiple servers with locally attached storage. Recognizing the dramatic performance gains achieved by data-centre and large departmental SAN implementations, IT managers now seek to extend data centre SAN advantages to smaller NT and Unix servers at the workgroup level or "edge" of the IT infrastructure. With foresight and planning, IT managers can create an enterprise-to-edge wide SAN by consolidating these edge devices into "mini" SANs and then connecting into the data centre backbone, creating a new resource with unparalleled productivity gains and operational efficiencies. Life at the Edge With all of its advantages, the data centre SAN serves only 40% of all data within the enterprise. The remaining 60% is stored in the numerous NT and Unix servers located in workgroups at the edge of the IT infrastructure. With "edge" data becoming increasingly more mission-critical, the majority of a company's most valuable asset - data - is largely unprotected and unavailable. Where workgroups were once able to tolerate a few hours of downtime, the seemingly trivial loss of e-mail now causes significant productivity losses, as workers are dependent on data access. The unavailability or outright loss of edge data can have a significant impact on the organization's bottom line. The cost and time involved in managing edge devices also impacts the organization's bottom line. While IT managers can allocate data centre storage resources across the SAN with a few keystrokes, they must travel to an edge server and tear into it to install more storage - idling numerous users in the process. Moreover, IT managers can not assure that backups are tested, reliable, and performed regularly at the edge. Managing edge data remains largely reactive rather than proactive, due to the distance and logistics of overseeing locally attached storage that resides in separate islands of technology.
Most of these islands utilize a direct-attach configuration where a small number of servers are attached via SCSI topology to a disk array or their own internal storage. SCSI-based configurations have severe distance, speed, and scalability limitations. To overcome these limitations, some configurations take advantage of Fibre Channel Arbitrated Loop (FC_AL) technology. FC_AL greatly mitigates speed and distance limitations. Devices on the loop can access other devices up to 500 meters away utilizing optical fiber - a definite improvement over the 30 meters allowed in SCSI topology. Devices also have up to one gigabit per second (1Gb/s) of available bandwidth to share. While scalability is also greatly improved when utilizing FC_AL, all devices on a loop must share the 1Gb/s bandwidth. Once the addition of new devices reaches the 1Gb/s bandwidth limit any further scaling of the system will result in decreased performance as devices are blocked from sending their data until the line clears. This limitation must be taken into consideration when designing a SAN that utilizes FC_AL so as not to exceed the bandwidth limitations on any one loop. Workgroup or "Mini" SANs How can IT managers improve protection of edge data that resides in isolated islands of loop technology? The immediate and obvious solution is to consolidate several NT or Unix servers, creating a localized "mini-san", where several NT or Unix servers are connected to common storage and backup devices. While improving scalability and incrementally improving backups, mini SANs do not eliminate remote management issues, allow for data sharing, nor provide for a future enterprise-toedge integrated storage resource. The advent of mini SANs is largely a result of available technology. Servers are attached to one of two types of connectivity devices - either a switch or a hub. Switches offer predictable high data transfer speeds, yet are significantly more expensive. Switches are utilized in the data centre or large departmental SANs, because they offer an unrestricted one gigabit per second (Gb/s) full duplex continuous data transfer between every server and storage connection. Hubs are far less expensive devices and are used where all connected servers and storage can share a one Gb/s throughput, taking turns transferring data. Unfortunately, a hub-based SAN has limited ability to scale. As bandwidth requirements of attached servers increases, the network quickly reaches the limit of the shared one Gb/s bandwidth available. These two options force IT managers to choose between cost and performance when selecting a connectivity device for the edge. The Ideal Solution With only hubs and switches available, expanding beyond mini SANs to an enterprise-to-edgewide SAN has been an elusive goal. While hub-based mini SANs can be inexpensively established at the edge, consolidating these mini SANs, and then connecting back to the data centre remains an issue. Thus, these mini SANs remain isolated islands of storage, unable to share data or storage resources. Connecting every edge device to a switch is an alternative - however it is an overkill approach that is cost-prohibitive. The ideal solution for interconnecting edge servers and storage calls for a device that combines the low cost of a managed hub with the essential switch features that allow connection to the data centre SAN backbone. Such a product would enable the cost-effective extension of data centre SAN advantages to workgroup servers and storage. Additionally, this ideal product should cut administrative costs and integrate seamlessly into the existing data-centre management platform. Organizations with existing hub-based SANs realize numerous benefits by moving to a switching product with combined managed hub and fabric switch features as described above. Legacy devices that were once only capable of connecting to a hub can now be an enterprise resource. SAN connection allows true any-to-any access for all IT assets - greatly improving their utilization. All devices in the enterprise can now be managed from a single location with a single, comprehensive
management tool. Most importantly, individual "mini-sans" can now participate in the enterprise SAN. Edge-In or Data Centre-Out? There are two distinct approaches to establishing the enterprise-to- edge SAN - starting from the data centre and building out to the workgroup or "edge," or building from the edge in to the data centre. A data centre-out design provides for long-term planning towards the creation of an enterprise-to-edge storage resource. The edge-in approach occurs by only reacting to immediate problems. SANs are built inward from the edge by simply responding to individual storage needs. This leads to numerous mini SANs that are difficult to consolidate into an enterprise-wide SAN. Each mini SAN must be individually managed and monitored. Furthermore, the mini SANs cannot share data or resources and they are not easily scalable. Using a data centre-out design recognizes the necessity of having a SAN backbone to accommodate a growing enterprise SAN. The SAN backbone is the point where all workgroup and departmental SANs connect allowing for convenient, centralized backups, and data and resource sharing. As the SAN grows, the backbone will become increasingly mission-critical as the enterprise becomes dependent on it for data access. The data centre SAN frequently serves as the larger enterprise-to-edge SAN backbone, using high availability and high performance director-class switches. This SAN, already serving mission-critical applications, is designed to offer a very high level of continuous uptime - often less than five minutes of downtime per year. Additionally, because of its design, the data centre SAN easily scales to incorporate workgroup and department mini-sans. By establishing the enterprise-to-edge wide SAN from the data centre out to the workgroup (edge), data center advantages are extended to edge storage. This provides the optimal degree of security, predictable backups, and experienced management techniques. Data center SANs have highly reliable backup systems that can be applied to protecting edge data. Data center IT managers can now apply their experience to improving edge security, storage management, and planning as well. Implementing the Enterprise-to-edge SAN With the SAN backbone in place, individual workgroup SANs can be rapidly incorporated into an enterprise-to-edge SAN by connecting each mini SAN to the backbone. Workgroups realize immediate benefits, as backups and data restorations are faster and more reliable. Productivity increases, as the need to take applications down for backups disappears. Downtime related to maintenance and expansion is eliminated. As the enterprise-to-edge SAN grows, the advantages of edge switches become increasingly evident. IT managers are now able to oversee all SAN resources from a central location, taking advantage of integrated software applications which manage the entire SAN. Workgroups are able to effectively share data and storage resources at high speeds not previously possible over the Ethernet LAN. Storage resources can be purchased to address multiple workgroups and departments at a time. Storage is allocated from a general pool to precise immediate needs, rather than liberally expanding servers one at a time. Summary An enterprise-to-edge wide SAN provides the most efficient, cost-effective, and productive solution to current and future storage needs. By shifting IT's focus from processor-centric to storage-centric, the inherent value of the enterprise data is increased as it becomes more available and more widely shared.
The key to implementing an enterprise-to-edge wide SAN is a cost-effective edge device closely tailored to the workgroup - low cost local connectivity combined with a means for enterprise integration.