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Table of Contents Table of Contents ......................................................................................................................................iii Table of Figures ........................................................................................................................................vii Table of Tables ........................................................................................................................................
Hitachi Data Systems Advanced Cache Algorithms of the Lightning 9900 Series ......................................................................18 Hitachi FlashAccess Allows Datasets to be Permanently Placed in Cache ................................................18 Read-ahead for High-performance Sequential Reads ................................................................................18 The Control Memory Hierarchical Star Network ................................................................
Chapter 9 – The Lightning 9900 Series Software Solutions Are the Best in the World ______________33 Increased IT service levels in availability and performance through Business Continuity Planning (BCP) software and services......................................................................................................................34 Remote Copy, Data Duplication, Data Migration Defined ......................................................................35 Remote Copy ............................
Hitachi Data Systems Hitachi NanoCopy Implementation Service......................................................................................46 Continuous Availability Service ........................................................................................................47 On-line Data Migration Service ........................................................................................................47 SAN Services ........................................................................
Table of Figures Figure 1 The 9960 provides for exploding growth and data consolidation while the 9910 provides for managed growth and open system exploitation. ................................................2 Figure 2 The Hitachi Lightning 9960 Series’ Hi-Star internal switched-fabric architecture.................3 Figure 3 System block diagram of the 7700E’s shared bus architecture. ..............................................4 Figure 4 A 9960 Control Frame and its major components. ............
Hitachi Data Systems Tables viii Table 1 Comparison of the Lightning 9900 series models. ................................................................2 Table 2 Bandwidth of supported interfaces of the Lightning 9900 Series. ......................................14 Table 3 System Capacities and Number of disk drives for various configurations. ..........................23 Table 4 Summary of Hitachi Freedom Storage software products and the business objectives they serve. ........................
Introduction The Only Switched-Fabric Storage Architecture in the World The Hitachi Freedom Storage™ Lightning 9900™ Series internal switched-fabric storage architecture is considered the most advanced design available in the world for open systems and mainframe data. The patented Hi-Star™ architecture powers the most intelligent, highest performance enterprise-class storage product in the industry today. 1.
Hitachi Data Systems Table 1 – Comparison of the Lightning 9900™ Series models.
Introduction Figure 2 – The Hitachi Lightning 9960™ Series’ Hi-Star™ internal switched-fabric architecture. At the heart of the Lightning 9900™ Series’ enormous capacity for throughput lies the Hi-Star™ architecture. This network of interconnecting high-speed links to system components provides an unequaled internal aggregate bandwidth of 6.4GB/sec (gigabytes/sec) in the 9960. This bandwidth is divided equally into 3.2GB/sec for data transfer and 3.
Hitachi Data Systems Comparison to the Shared Bus Architecture of the Hitachi Freedom Storage™ 7700E Bus contention is virtually eliminated with the Hi-Star™ Architecture. Unlike the shared common bus architecture of previous generation storage products, such as the 7700E (as shown in Figure 3 for reference to a shared bus architecture), Hi-Star™ is designed to truly scale in both capacity and performance.
Introduction Other Information Sources Available from Hitachi Data Systems® Additional information on the enterprise storage market, including an in-depth overview of the technically advanced and unsurpassed software solutions available from Hitachi, is available in the companion publication, the Hitachi Software Solutions Guide. This document is downloadable in PDF format from www.hds.com.
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The Lightning 9900 Series Packaging 2 Model 9960 Packaging The Lightning 9960™ is available in a two to seven cabinet configuration (as shown on the cover of this guide), depending on connectivity and capacity needs. A Control Frame serves as the control center of each system and manages up to six Array Frames that are connected via high speed Fibre Channel links. A fully configured system is contained in seven cabinets 70.5 inches high, 171.3 inches wide, and 31.5 inches deep.
Hitachi Data Systems Model 9960 Array Frames Array frames 1-4 of the 9960 contain up to 96 Hard Disk Drive Assemblies (HDDs) and communication interfaces to the Control Frame. Array frames 5-6 contain up to 64 drives for a total of 512 drives for a maximum configured system. An Array Frame is shown in Figure 5. This design allows for efficient centralized and consolidated storage, which results in reduced management costs and lower overall total cost of ownership.
The Lightning 9900 Series Packaging Cables carry 48-volt main system power from the back of the Control Frame and Array Frame where the power is converted to the required voltages. Different AC power cord options allow all Lightning 9900™ Series models to connect with the different electrical outlet configurations used around the world. Figure 6 – A power supply module of a Lightning 9900™ Series system.
Hitachi Data Systems Figure 7 – A 9910 single-cabinet storage subsystem. The System Monitoring Network of the Lightning 9900™ Series The Lightning 9900 ™ Series systems have both a predictive maintenance and a failure alert system. 10 The Lightning 9900™ Series systems are designed with a system-monitoring network.
Front-end Design of the Hitachi Lightning 9900 Series 3 CHIPs Support Fibre Channel Host and ESCON® or FICON Host Connectivity and Scalability The Lightning 9900™ Series supports both Fibre Channel for open systems and ESCON® or FICON for S/390® compatible platforms as shown in Figure 8. Figure 8 – Fibre Channel and ESCON® or FICON adapter boards connect to open systems and mainframe computers.
Hitachi Data Systems About the Fibre Channel Interface Boards Each Fibre Channel Interface Board, as shown in Figure 9, has four Interface Processors2 for management of connectivity to the host. Figure 9 – A Fibre Channel host adapter board and its major hardware components. 12 2 The Lightning 9900™ Series uses the Reduced Instruction Set (RISC) Intel® i960 80MHz processor that is especially designed for I/O operations.
Front-end Design of the Hitachi Lightning 9900 Series There are four ports for each interface board or a total of 32 host interfaces for a fully configured system. An ESCON interface board is shown in Figure 10. A FICON interface board has a similar appearance. Figure 10 – An ESCON® host adapter board and its major hardware components.
Hitachi Data Systems Figure 11 – A 9960 system connected to Mainframes and Open Systems hosts. Bandwidth of Supported Host Interfaces The bandwidth of interfaces supported by the Lightning 9900™ Series is shown in Table 2. Table 2 – Bandwidth of supported interfaces of the Lightning 9900™ Series. Supported Interface Bandwidth Fibre Channel Adapters 100MB/sec or 200MB/sec ® ESCON Adapters 17.
Hi-Star Architecture – An Internal Switched Hierarchical Star Network 4 The Internal Hi-Star Architecture The internal Hi-Star architecture consists of two separate networks, the Cache Hierarchical Star Network (C-HSN) and the Control Memory Hierarchical Star Network (CM-HSN). The Cache Hierarchical Star Network The C-HSN is the network used for transferring data to and from the main global data cache.
Hitachi Data Systems The Cache Switch Provides Non-blocking Switched Access to Cache The CSW is at the heart of the Lightning 9900™ Series. At the heart of the C-HSN is the Cache Switch (CSW). Together, these four switches (in the 9960) form the internal start using parallel switch fabric bus (PSFB) of the C-HSN. The CSW is a specially designed crossbar switch that functions as a combination MUX, path arbitrator, and non-blocking network switch.
Hi-Star Architecture – An Internal Switched Hierarchical Star Network Figure 14 – A shared-bus architecture is limited to two simultaneous I/O operations. In a shared bus storage system, the number of internal simultaneous processor operations that can occur is equal to the number of buses on the backplane. The shared buses are used by all host channels to communicate between the processors on the host adapters and cache memory.
Hitachi Data Systems The 9960 Provides 32GB of Fully Addressable Cache The 9960 supports up to 32GB of data cache, all directly addressable. Separate cache modules (up to 1.5GB) are used for control storage. Competitive systems use their cache for both data and control information, limiting the amount of usable data cache. Advanced Cache Algorithms of the Lightning 9900™ Series The Lightning 9900™ Series has a variety of advanced cache algorithms and software solutions that allow exceptional performance.
Hi-Star Architecture – An Internal Switched Hierarchical Star Network control memory in its “split” configuration. Again, control memory is mirrored. This path topology is used to facilitate this mirrored architecture. Either way the bandwidth is calculated in the CM-HSM, the bandwidth is 3.2GB/sec total when all of the processor modules are installed. 4 bits clocked at 100MHz equals 50MB/sec per path multiplied by 64 ports is 3.2GB/sec bandwidth.
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High Performance Back-end Design 5 High-speed Back-end Design New Hitachi high-performance back-end drives are available with the Lightning 9900™ Series. The drives are attached via Fibre Channel – Arbitrated Loops (FC-AL). Eight 100MB/sec FC-AL connect to dual ported drives for each ACP pair. With four configured ACP pairs installed (at 800 MB/sec per ACP pair) that’s 3.2GB/sec total back-end bandwidth to the physical drives.
Hitachi Data Systems These new dual-ported/dual-active Fibre Channel disk drives, combined with the technology built into the ACP pair, allow the back end of the Lightning 9900™ Series to use all eight FC-AL paths in an ACP pair for both performance and fault tolerance. However, no one disk or array group can use both paths simultaneously. The ACPs monitor the activity and the utilization of the paths. Based on this information, the ACPs determine the best path to use for accessing a disk.
Capacities and RAID Architecture 6 Storage Capacity of the Lightning 9900™ Series The Lightning 9900™ Series supports an unmatched range of capacities as shown in Table 3. System Capacities and Number of disk drives for various configurations Raw System Configuration Raw capacity with 18GB drives Raw capacity with 73GB drives Raw capacity with 180GB drives Lightning 9960 One Array Frame 1.7TBs = 96 disks 7.0TB = 96 disks 16.6TB = 96 disks Lightning 9960 Six Array Frames 9.4TB = 512 disks 37.
Hitachi Data Systems Figure 20 – The Lightning 9900™ Series systems are available with RAID-1+ and RAID-5 arrays. High-density Disk Drive Assemblies (HDDs) Each drive has the industry unique feature of supporting dual active ports. 24 The disk drives used in the Hitachi Lightning 9900™ Series are specially designed for high availability and performance by Hitachi Limited. Each drive has the industry unique feature of supporting dual active ports. This provides significantly increased performance.
Hitachi High-Availability Software Improves Application Service Levels 7 An Overview of High-Availability (HA) Computing Software It is increasingly important for a business to support continued access to global information 24 hours a day, 7 days a week. What’s more, careers often depend on the availability of service levels provided by IT to the enterprise. In computer science, availability refers to the degree to which a system or resource is capable of performing its normal function.
Hitachi Data Systems Hitachi is the only major supplier of enterprise class storage systems with a 100% availability guarantee. • Dual data paths and dual control paths connecting every component. • Mirrored cache for all write data instead of single image cache. • GDPS support. • Hitachi TrueCopy combined with ShadowImage™ for disaster recovery. • Hitachi NanoCopy™ to provide Point-in-Time copies without requiring quiescence of databases or applications.
Hitachi High Availability Software Improves Application Service Levels There are four basic types of high-availability middleware that can reduce downtime in the event of a data path or host failure. The Lightning 9900™ supports each classification of middleware: 1. Alternate Pathing middleware switches the I/O load in the event of path failure This type of middleware automatically switches the I/O load on a failed primary path to an alternate path on the same host system.
Hitachi Data Systems Figure 22 - Hitachi Dynamic Link Manager™ automatically provides path failover and load balancing for open systems. 4. Parallel Database Clustering Clustering middleware supports distributed lock management. This type of middleware is a special version of host failover middleware, which supports major parallel database servers like Oracle® Parallel Server, Informix® XPS, and Sybase® MPP.
Hitachi High Availability Software Improves Application Service Levels Standard Redundant Fans for Cooling The Lightning 9900™ provides fully redundant fans for uninterrupted cooling to all components of the system. The speed and operation of these fans are monitored by the environmental monitoring system. If a fan should fail, it can be “hot swapped” without disruption to the cooling system.
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Performance Considerations Truly Scalable Performance Based on the internal switched-fabric Hi-Star™ architecture, the Lightning 9960™ shows unmatched performance scalability. The more capacity and connectivity added to the 9960, the more total bandwidth increases. As stated previously, the 6.4GB/sec internal bandwidth is reached when all 16 modules are installed and functioning.
Hitachi Data Systems Internal Switching Overcomes the Limitations of Shared Bus Architectures Bottleneck-free performance with the Lightning 9900™ Series. It can be seen from Figure 24 that a reduction occurs in the OLTP performance for the shared bus architecture of the 7700E system. This occurs at Point 1, when the DSS application begins at about 45 minutes into the test.
The Lightning 9900 Series Software Solutions Are the Best in the World 9 Customers and analysts regard the Hitachi Freedom Storage Lightning 9900™ Series as the most advanced products in the enterprise storage system market. The Software Solutions Guide discusses the advantages of this suite of leading-edge software products that enhances the Lightning 9900™ Series product lines. This report is available from Hitachi Data Systems in PDF form http://www.hds.com/products/software/solutions_guide .html.
Hitachi Data Systems The Hitachi Freedom Storage™ software solutions for Lightning 9900™ Series systems support an enterprise’s strategic goal of accessing any information, on any computer, located anywhere, at any time. The many advanced functions available on Lightning 9900 Series™ hardware are initiated, managed, and controlled through these powerful software programs. Table 1 summarizes how Hitachi software solutions can be mapped to the business benefits mentioned above.
The Lightning 9900 Series Software Solutions are the Best in the World To this already robust platform, Hitachi Data Systems adds a number of solutions to ensure quick recovery from acts of nature, human errors, application errors, and malicious attacks. In the world of e-commerce, it is no longer enough to have a backup copy of one’s data; businesses must also plan for rapid recovery from such outages.
Hitachi Data Systems Business Goals served by Copy Software Real-time/point-in-time copies heighten both data security and mobility for a variety of critical activities, including protection, testing, disaster recovery, and warehousing. Worldwide commerce and industry have become increasingly dependent on IT resources to conduct business. Even a temporary loss of critical applications or data access can cause serious economic impact to a company, and an extended outage can threaten a company’s existence.
Centralized and Open Systems Management Software Simplifies IT Operations 10 A powerful and open systems management philosophy The Hitachi Freedom Storage® software solutions support an enterprise’s strategic goal of helping customers focus on their business issues instead of on deploying enabling technologies by providing powerful centralized management capability.
Hitachi Data Systems Figure 25 HiCommand™ allows management of virtually all Hitachi hardware and software from the customer’s platform of choice. HiCommand™ enables an enterprise to manage Hitachi storage products and software solutions. HiCommand™ is an important Hitachi management tool in that it provides a comprehensive storage management software framework that enables an enterprise to manage all supported Hitachi storage products and many Hitachi software solutions: 1.
Centralized and Open Systems Management Software Simplifies IT Operations The components of HiCommand™ HiCommand™ consists of three components: 1. The HiCommand™ Server resides on any Windows® NT/2000, or Sun Solaris server, and connects to the Lightning 9900™ Series system(s) over a private LAN.
Hitachi Data Systems Hitachi Resource Manager™ 9000 The following is a summary list of the many ways in which the Hitachi Resource Manager™ can simplify IT operations, improve availability and performance service levels for business critical OLTP and DSS applications, and thereby enable the more rapid deployment of new applications by managing data more intelligently.
Centralized and Open Systems Management Software Simplifies IT Operations information at the touch of a button. The robust GUI-oriented command screen for Hitachi Graph-Track™ is shown in Figure 26. Running on a PC attached to a dedicated LAN, Hitachi Graph-Track™ displays real-time or historical data for all connected Lightning 9900™ systems, helping users identify important peaks in utilization and ongoing trends in processing.
Hitachi Data Systems Hitachi LUN Manager also features logical unit size expansion that dramatically improves LUN flexibility. Up to 36 physical LUNs can be presented to the operating system as a single, large LUN. This capability simplifies storage management because there are fewer LUNs to manage. Two levels of password protection, user and administrator, ensure maximum data security.
Centralized and Open Systems Management Software Simplifies IT Operations Storage Maximizer The Hitachi Storage Maximizer™ is a solution that uses two software products – Hitachi CruiseControl™ and Hitachi FlashAccess™ software for mainframes and open systems. This allows customers to manage the cost of storage, as data is consolidated onto fewer better-managed systems.
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Professional Services and Support 11 Hitachi Data Systems® is consistently ranked Number One in the Industry In numerous independent surveys on IT services organizations, Hitachi Data Systems® continually wins the highest ratings in terms of overall customer satisfaction.
Hitachi Data Systems order to protect it. The Data Protection Services team uses software in all three categories of data movement: 1) Data Migration 2) Real-Time Copy 3) Point-in-Time Copy The team will perform data relocation and migration tasks that establish rock-solid backup and disaster recovery copy facilities to keep a business running in the event of man-made or natural disaster. Often the need for an enterprise to allocate staff for these tasks is eliminated.
Professional Services and Support Continuous Availability Service Keeping critical systems available at a level 4 or 5 on the Scale of 9s is no easy task. It involves the best of hardware, software, and operations practice. Hitachi Data Systems® professional services experts review the entire backup and recovery software portfolio, operations procedures, and hardware configurations of the enterprise. Weaknesses that threaten the IT environment are then systematically analyzed and eliminated.
Hitachi Data Systems Hitachi Data Systems® offers an entire suite of professional services that will assist clients in planning and implementing Storage Area Network (SAN) solutions to optimize management and control data across the enterprise.
System Configurations for the Performance Experiment A Configurations of the HP and Sun Servers and Configurations of the Lightning 9960™ Switched Architecture to a Shared-bus Architecture like most competitive products for the Performance Experiment In the performance test discussed in Chapter 8, comparing each application resided on its own array groups. The only resource shared by the application is the storage controller (cache, paths, etc.), and two ACP pairs (there are four ACP pairs total).
Hitachi Data Systems differences between the 7700E and the Lightning 9960™ system for the DSS workload; 50 • The 7700E used all 6GB drives. • The Lightning 9960™ system used a mix of 18GB and 47GB drives.
Glossary of Terms 10BaseT Ethernet with a data transfer rate of 10Mbits/sec. 100BaseT Also known as Fast Ethernet with a data transfer rate of 100Mbits/sec. AG Array Group. ACP Array Control Processor. The group of processors on a PCB that performs the physical access of the disk drives across four FC-AL loops. ACP pair A combination of two ACPs. Designed in such a manner as to facilitate redundancy and performance.
Hitachi Data Systems communication is an exactly timed stream of bits when the start of a character is located by using a clocking mechanism such as bipolar encoding. See also Synchronous, Hitachi TrueCopy™. Availability In computer science, availability refers to the degree to which a system or resource is capable of performing its normal function. Availability is measured in terms of Mean Time Between Failure (MTBF) divided by MTBF plus the Mean Time to Repair (MTTR).
Glossary CARB Cache memory Arbitrator circuit. Hitachi designed logical circuit in the Cache Switch (CSW) used to arbitrate access to cache. Cache Cache (pronounced cash) can be either on-chip memory circuits in a microprocessor (e.g. L2 processor cache), a reserved section of main memory (e.g. system or server cache), or an independent, high-speed disk storage device (e.g. a Web cache). Two types of caching are commonly used in personal computers: memory caching and disk caching.
Hitachi Data Systems Consistency Groups A software copy technique of suspending multiple volumes at the same time. Control Frame The Disk Controller or control frame, is the center cabinet of the Lightning 9900™ Series system, housing the channel switch, cache, power supplies, batteries, and host interface cards. CORA (Cost of Risk Analysis) CORA is a unique, software-based risk management system developed initially for the insurance industry by International Security Technology (IST) Inc.
Glossary DD Disk Director. Data Duplication Software that duplicates data as in remote copy or Point-in-Time (PiT) snapshots. Data duplication is differentiated from data migration in that with data duplication at the end of the process there are two copies of data and with data migration there is only one. Data Migration Software that migrates data from one storage device to another. This feature is different from data duplication in that at the end of the process there is only one copy of data.
Hitachi Data Systems EBCDIC Abbreviation of Extended Binary-Coded Decimal Interchange Code. Pronounced eb-sih-dik, EBCDIC is an IBM® code for representing characters as numbers. Although it is widely used on large IBM® computers, most other computers, including PCs and Macintoshes®, use ASCII codes. See also ASCII, binary, synchronous, and asynchronous. Electronic vaulting The transfer of data to an offsite storage facility via a communication link rather than via portable media.
Glossary Failover Host, host bus adaptor, cable, or controller failover is the routing of all transactions to a second controller when the first controller fails. Fast Ethernet Fast Ethernet or 100BaseT, defined by the IEEE 802.3 standards committee, provides a 100 Mbps standard that is compatible with existing 10BaseT installations, preserving the CSMA/CD media access control (MAC) protocol. Fast write A write operation at cache speed that does not require immediate transfer of data to a disk drive.
Hitachi Data Systems log in with each other and the switch to exchange operating information on attributes and characteristics. This information includes port names and port IDs and is used to establish interoperability parameters. FICON An ESA/390® computer peripheral interface. File Backup The practice of copying a file that is stored on disk or tape to another disk or tape is referred to as file backup. This is done for protection in case the active file gets damaged.
Glossary run concurrently. Reliability is enhanced with retry logic, alternate path routing, and restart from point of failure. Ease of use is provided by a Java-client interface, a system monitor, scheduling support, and remote control of client functions from OS/390®. HDD High-density disks. Used in the Lightning 9900™ Series.
Hitachi Data Systems storage ports, multiple cache nodes, and multiple disk Array Control Processors (ACPs). Each path runs at 100MB/s, permitting the Lightning 9900™ to scale up to a total bandwidth of 6.4 GB/s. This is six-to-eight times the internal bandwidth of shared bus based storage systems. For redundancy and performance, Hi-Star™ consists of four cache switches that are cross-connected to four cache modules and two control memory banks.
Glossary Hitachi Rapid Recovery The Hitachi Rapid Recovery solution for S/390®-attached storage combines Hitachi NanoCopy™, Hitachi TrueCopy-S/390 Asynchronous™, and Hitachi ShadowImage™. This facility enables data to be copied from one set of S/390®-attached systems to another with complete transaction integrity and without disrupting user applications in any way.
Hitachi Data Systems HSN Hierarchical Star Network. The technical term used to describe the combined internal networks (the C–HSN and the CM–HSN) of the Lightning 9900™ Series. Hub A common connection point for devices in a Fibre Channel network. A hub contains multiple ports. When a Fibre Channel packet of data arrives at one port, it is copied to the other ports so that all storage devices on a SAN can see all packets.
Glossary Lightning 9900™ Series The Lightning 9900™ Series was announced in June 2000 (Lightning 9960™) and November (Lightning 9910™). It represents a major advance in enterprise-class storage systems with its Hierarchical Star Network switched internal architecture, which provides for many times more simultaneous transfers to and from the host compared to shared bus architectures. Logical Unit The SCSI term for a logical disk drive. Logical Unit Number See LUN.
Hitachi Data Systems MBCP Master Business Continuity Professional. The highest level of professional certification of the Disaster Recovery Institute (DRI). The master level targets an individual with a minimum of five years of experience as a business continuity/disaster recovery planner. See also DRI (Disaster Recovery Institute), CBCP (Certified Business Continuity Professional), and ABCP (Associate Business Continuity Professional).
Glossary MTBF Mean Time Between Failure. A commonly used measure of system reliability, usually expressed in hours. Modern disk drives typically have an MTTR of 1 million hours or more. MTTR Mean Time To Repair. Includes the time taken to diagnose the failure, replace or repair faulty component(s) and restart the system so it is available to users. See MTBF.
Hitachi Data Systems On-line system An interactive computer system supporting users over a network of computer terminals. Open system A system whose characteristics comply with standards made available throughout the industry, and therefore can be connected to other systems that comply with the same standards. Operating System The operating system is the most important software program that runs on a computer.
Glossary RAID Redundant Array of Independent Disks. RAID is used to increase the reliability of disk arrays by providing redundancy either through complete duplication of the data (RAID-1, i.e., mirroring) or through construction of parity data for each data stripe in the array (RAID-3, -4, -5). RAID-5, which distributes parity information across all disks in an array, is among the most popular means of providing parity RAID since it avoids the bottlenecks of a single parity disk.
Hitachi Data Systems SCSI Small Computer System Interface. An intelligent bus-level interface that defines a standard I/O bus and a set of high-level I/O commands. There are currently many flavors of SCSI defined by different bus widths and clock speeds. The seven major variations of SCSI are SCSI 1, SCSI 2 (Fast/Narrow), SCSI 2 (Fast/Wide), Ultra SCSI (Fast/Narrow), Ultra SCSI (Fast/Wide) – also called SCSI 3, Ultra 2 SCSI (Narrow), Ultra 2 SCSI Wide. See also Fibre Channel.
Glossary Synchronous Synchronous communications occurs when the transmission of data between two devices is synchronized with a clocking scheme or other technique. The sender and receiver need to synchronize with one another before data is sent. In synchronous communication the bit stream and the clock pulse are synchronized by a special bit transition pattern in the digital signal creating an exactly timed stream of bits from the sending device to the receiving device.
Hitachi Data Systems WAN Wide Area Networks or WANs are networks of computers that are geographically dispersed and connected by radio waves, telephone lines, satellites, or high-speed fibre optic backbones. Warm site An alternate-processing site that is only partially equipped (as compared to Hot site which is fully equipped). See also Hot site and Cold site. Workload I/O workload refers to the pattern of I/Os presented to the Lightning 9900™ Series system or to a disk drive. XRC Extended Remote Copy.
Hitachi Data Systems Worldwide Offices Hitachi Data Systems is registered with the U.S. Patent and Trademark Office as a trademark and service mark of Hitachi, Ltd. The Hitachi Data Systems logotype is a trademark and service mark of Hitachi, Ltd. www.hds.com www.storage@hds.
