PARTNER TECHNICAL BRIEF Storage Designed for Availability Dot Hill AssuredSAN™ & SANsymphony™-V Dot Hill AssuredSAN Designing a data storage infrastructure for high availability requires the selection of 12-bay & 24-bay systems the most reliable hardware components, coupled with intelligent data management software to assist recovery of critical business data regardless of the cause of failure. Solution Highlights This paper outlines the design techniques employed to achieve high availability in the Dot Hill AssuredSAN series of storage arrays with an overview of the methods ● Virtualized storage enables seamless failover (HA) and WAN of replication available within the DataCore SANsymphony-V platform. replication (DR) ● Test function allows for simulated DataCore Ready Certified disaster recovery The combination of SANsymphony-V and Dot Hill AssuredSAN storage arrays ● Eliminates single points of failure which are certified under the rigorous DataCore Ready Program offers a rock solid storage foundation built upon storage hardware designed for availability and a data Dot Hill AssuredSAN management layer providing both asynchronous and synchronous replication. Highlights Keeping Users And Applications Running Undisturbed ● DataCore Ready certified ● Demonstrated 99.999% Highly reliable storage hardware is a vital foundation for business continuity availability but many IT organizations fail to account for the multitude of other factors ● Designed for high availability that greatly contribute to business upheaval. DataCore storage virtualization software prevents these more frequent sources of storage-related disruptions ● NEBS & MIL-STD-810G compliant from ever affecting applications and we enable you to do this in a cost-effective manner that leverages a variety of different devices for redundancy. ● Certified with VMware ESX, vSphere, Microsoft and Citrix Xen Server The Datacore Ready Program Value Proposition DataCore Ready identifies solutions trusted to strengthen SANsymphony-V- based infrastructures. While DataCore solutions interoperate with common open and industry standard products, the DataCore Ready designation ensures that these solutions have successfully executed a functional test plan and additional verification testing to meet a superior level of joint solution compatibility. Customers who leverage DataCore Ready offerings benefit from quality assurance, reduced risk and lower integration costs. The DataCore Ready logo helps customers quickly identify products and solutions that are optimized for SANsymphony-V. Designing for High Availability High availability for the Dot Hill storage arrays is achieved through a combination of three design elements: • High reliability (measured by the Mean Time Between Failures or MTBF) of the complete system • Redundant subsystems to eliminate as many single points of failure as possible • Rapid repair of any failure (measured by Mean Time to Repair or MTTR) by using Field Replaceable Units Dot Hill’s mechanical design enables the power supply and fan, I/O module and controller, and disk (FRUs) for all critical subsystems. drives all to be serviced quickly as hot-swappable Field Replaceable Units (FRUs). Being able to replace redundant FRUs while the system is fully operational further enhances availability. The following equation for availability demonstrates the vital role of serviceability in the system’s design. the availability of the system itself. Dot The second serviceability technique is Maximum availability can be achieved Hill’s AssuredSAN architecture features immediate notification of any failure. only by minimizing the time it takes full redundancy for every subsystem The longer it takes to detect a failure, to affect a repair, which is reduced requiring a significant number of the longer it will take to repair; this is significantly by using FRUs. active components. The mechanical rather obvious. Time is of the essence chassis itself cannot be redundant, of for another reason, however: The failure Availability = MTBF course, and there is a single mid-plane of a redundant subsystem creates, in that performs the simple function of effect, a temporary single point of failure MTBF + MTTR connecting the redundant controllers that increases the risk of a system-level to the redundant disk drives. The mid- outage. For this reason, the firmware in To achieve maximum availability, Dot Hill plane has minimal active components, all Dot Hill systems is designed to detect, designs for reliability and serviceability, however, and Dot Hill selects these for isolate and confirm any failure, initiate as well as for manufacturability. the highest possible reliability. The result a fail over to a redundant subsystem, is an extraordinarily high MTBF for the and provide immediate notification. The Design for Reliability & chassis and its mid-plane, and therefore, actual “messaging” of the notification can Serviceability (DFRS) virtually no impact on system availability. also be configured to match operational Designing hardware for high reliability procedures to ensure that on-duty and serviceability involves both the Modular FRU Design with staff is properly and quickly notified. system and its subsystems. To achieve Rapid Fault Notification high availability at the system level, To enhance system serviceability Designing for Maximum MTBF Dot Hill integrates reliability into for the shortest possible MTTR, Dot At the FRU or subsystem level, Dot Hill the design process in several ways. Hill utilizes several complementary utilizes four separate design techniques The first and most obvious is the design techniques. The first is the use to maximize the MTBF of each, while use of disk drive redundancy with of a modular chassis with FRUs. The at the same time also maximizing the RAID configurations and dual power ability to swap out a confirmed failed inclusion of leading-edge SAN features. supplies, each including its own fan subsystem quickly and easily minimizes The first is reducing the part count. to prevent over-heating (and thereby, the time it takes to repair an installed Because any individual part can fail, the accelerated component failures). Even system and restore it to full operation. fewer there are, the higher the inherent higher availability is achieved by using By utilizing such a modular design, reliability of the subsystem. Dot Hill redundant controllers. By eliminating which provides convenient access to engineers endeavor, therefore, to single points of failure in these critical all subsystems, Dot Hill’s AssuredSAN minimize the parts required on all printed subsystems, the system itself continues products can be maintained seamlessly circuit boards and other subsystem FRUs. to operate normally during a failure of with minimal or no disruption in any single FRU. While such a failure does service during most repairs. factor into the subsystem’s MTBF (its rated reliability), it does not diminish 2 High Quality Components Ensuring Software Maturity DataCore Sync Mirroring for Lower TCO To maximize software reliability, Dot Having looked in detail at the techniques The second technique is to use only Hill monitors the improvement in the used to ensure storage hardware high quality parts. Higher quality parts Mean Time to Discovery (MTTD) of bugs availability we turn now to consider how cost more, of course, but their superior to assess the maturity of all software combination with DataCore’s storage performance and longer service lives and firmware during development. It is virtualization and management software normally contribute to a lower total cost important to note that MTTD is not an delivers a deployment architecture where of ownership in the long-run. Despite industry metric, but is instead a software single points of failure are eliminated. the higher per-part cost, minimizing the maturity metric created by Dot Hill as Synchronous mirroring handles the part count, while concurrently enhancing part of the company’s commitment real-time replication of I/Os providing functionality, helps to improve the to quality and reliability. All designs the ultimate in continuous availability. overall price/performance of a highly- must have a sufficiently high and reliable design. For these reasons, Dot stable MTTD before being finalized. Sync mirror features include: Hill utilizes only the highest quality parts available from reputable suppliers. Stringent Design Verification • N+1 redundant grids for continuous availability The design is released to manufacturing • Eliminate SAN or storage as a single Increased Operating Margins only after passing three comprehensive point of failure when combined The third technique involves the de- tests. The Engineering Verification with host MPIO or ALUA drivers rating of selected parts. Operating any Test (EVT) and the Design Verification Test (DVT) ensure that the system and/ • Enhance survivability using physically part or component at or near its rated separate nodes in different locations capacities inevitably shortens its useful or subsystem(s) fully satisfy all design • Mirrored virtual disks behave like service life. For critical parts, Dot Hill specifications, including those for high one, multi-ported shared drive, selects only those that will be able to reliability of both the hardware and software. These tests also confirm while automatically updating the operate at approximately 50% of their two copies simultaneously maximum allowable specifications for that marginal variations in parts from voltage, power and/or