DISK LIBRARY FOR MAINFRAME Geographically Dispersed Disaster Restart Tape ABSTRACT Disk Library for mainframe is Dell EMC s industry leading virtual tape library for IBM zseries mainframes. Geographically Dispersed Disaster Restart (GD) Tape provides mainframe-based monitoring, alerting, and disaster restart capabilities for DLm in IBM z/os operating environments. This white paper is intended to provide an overview of GD Tape capabilities and explain the value that GD Tape provides customers using DLm for their tape library. February 2017 WHITE PAPER
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TABLE OF CONTENTS EXECUTIVE SUMMARY...4 Audience... 4 DISK LIBRARY FOR MAINFRAME OVERVIEW...4 GD OVERVIEW...6 GD TAPE MONITORING...7 TEST SETUP / TEARDOWN...8 FAILOVER / FAILBACK... 10 SWITCHOVER / SWITCHBACK... 10 GD FOR UNIVERSAL DATA CONSISTENCY TM... 10 SUMMARY... 11 3
Executive Summary Disk Library for mainframe is an industry-leading virtual tape library (VTL) for IBM and Unisys ClearPath Dorodo mainframe computers. Unlike other leading VTLs for mainframe, DLm is a disk-only solution storing tape volume (VOLSER) images on disk storage attached to the DLM virtual tape emulation system. As a disk-only solution, DLm does not rely on physical robotic tape libraries to provide data protection and/or disaster recovery. Typical DLm configurations include multiple DLms, usually in different physical locations, replicating their critical tape volumes (VOLSERs) between each other in order to provide appropriate data protection in the event of physical equipment failure or destruction. DELL EMC GD is a long-established, mainframe-based software automation package DELL EMC has used to provide equipment and environmental monitoring, alerting, and automated restart and recovery in IBM zos mainframe multi-site environments where EMC Symmetrix (VMAX) Direct Access Storage Devices (DASD) are in use. GD Tape provides similar monitoring, alerting, and restart capabilities to multi-site IBM zos environments where Disk Library for mainframe has been implemented. GD and GD Tape can be implemented separately or together to aid, enhance, and provide geographically dispersed disaster recovery for multi-site zos environments using both VMAX DASD and DLm storage systems. Audience This white paper is intended for IBM zos (mainframe) storage administrators, managers and decision makers. The purpose of this white paper is to provide an overview of capabilities available in GD Tape and how those capabilities can be used to provide an enhanced automated approach to DLm monitoring and restart in a two-site mainframe environment where DLm has been implemented. Disk Library for mainframe Overview Disk Library for mainframe (DLm) is a virtual tape library for IBM mainframes. DLm offers two separate models, the DLm2100 and the. DLm2100 is a single 2U rack mount system with 2 8 Gbit FICON interfaces capable of emulating 1 to 256 virtual tape drives. A typical DLm2100 environment consists of one or two DLm2100 controllers attached to a Data Domain storage subsystem with data protection provided by the DD storage replicating to a remote DD and DLm2100. Figure 1 shows a sample DLm2100 configuration implemented in a 2 site mainframe environment. Primary Secondary DLm2100 DLm2100 DLm210 0 Data Domain Data Domain Figure 1. Typical DLm2100 Deployment 4
is a large-scale virtual tape solution targeted at enterprise mainframe customers of all sizes. delivers a complete virtual tape solution. A scales from a single Virtual Tape Engine () with two 8 Gbit FICON interfaces emulating 256 drives up to a maximum of 8 s providing a total of 16 FICON interfaces and emulating up to 2,048 virtual tape drives. supports Data Domain, VNX, and/or VMAX storage systems for use as primary virual library storage space. Mainframes can scale their total virtual tape library capacity from a few TB of usable space to many PBs of storage, depending on which storage solution is implemented. For example, a using VNX storage can scale total usable capacity from approximately 20 TB to just over 3.1 PB. Combining that usable capacity with data compression rates of 3 to 1 or higher and a single DLm solution can satisfy a wide variety of demands. Primary Site Secondary Site Data Domain And /Or VNX, VMAX All Flash, VMAX3 Data Domain And /Or VNX, VMAX All Flash, VMAX3 Figure 2. Typical Deployment 5
As shown below in Figure 3, the DLm architecture consists of three distinct components, Virtual Tape Engines (s) providing the mainframe connectivity and tape emulation, one or more file services providing shared access to storage for multiple s, and the physical storage itself. File Service s File Service sssss Figure 3. DLm Architecture Each provides 2 FICON interfaces and emulates 256 tape drives. Multiple file service engines provided shared access to the storage so that a tape volume (VOLSER) written by a drive in one can be later accessed by a drive in a different. A DLm tape library is made up of multiple shared filesystems exported from one or more file services. A small DLm could be a single filesystem managed by a single file service. A large DLm library could be made up of 100s of filesystems being managed by multiple file service engines. Filesystems can be organized into storage classes within the library allowing tape volumes to be separated into groups based on class. For example, an application s tapes (such as payroll) could be separated into their own filesystems by writing those tapes to a different storage class. A common use for storage classes is to separate production tapes requiring data protection from work tapes requiring no protection. Filesystems in a production storage class would be replicated to a remote site, while filesystems in a work class would not be replicated. Individual filesystems can hold thousands of individual tape volumes. Disk Library for mainframe is a tape-on-disk solution. Unlike other virtual tape libraries where VOLSERs written by the mainframe are temporarily stored on a disk cache and then stacked on dense physical cartridges for permanent storage and data protection, DLm compresses data received from the mainframe and then permanently stores the VOLSER images on Dell EMC storage with data protection being provided via a combination of a Redundant Array of Independent Disks (RAID) and data replication between DLMs providing multiple copies of the data. GD Overview Geographically Dispersed Disaster Restart (GD) software is IBM mainframe-based software. provides two distinct capabilities. As shown in Figure 4 GD First, GD provides continuous monitoring of the storage and environment. When a disruption or failure is dectected, GD will automatically provide alerting to the mainfame operations staff that a disruption / failure has been detected. 6
Secondly, GD provides Disaster Recovery automation services. These services are provided via a collection of scripts that can be run on the mainframe to take specific actions and provides automation for both planned and unplanned events. Site 1 Site 2 Monitoring Monitoring Figure 4. GD essential Software function GD is offered in two distinct varieties. The original GD targets mainframe Direct Access Storage Devices (DASD); specifically Symmetrix (VMAX) FICON attached storage being used as the primary DASD in zos environments. This product, GD, includes support for high-end Disk Library for mainframe configurations where VMAX storage is being used as the DLm respository. Universal Data Consistency TM will be discussed later in this paper and allows VMAX DASD and DLM VMAX storage to be controlled together across two and three site configurations in order to provide single point in time data consistency between data stored on DASD and data stored in a DLm virtual tape library. GD Tape leverages the techonolgies developed for the full GD product to provide a cost effective solution for monitoring and providing automation for two site DLm environments when DLm is being used with VNX and/or Data Domain storage. GD Tape is intended to provide 3 basic services to two site DLm environments: 1. Monitoring of the DLm components with automatic Alerting when a non-standard condition is detected. 2. Automatic setup and tear down of a test environment allowing for testing to be done without disrupting production tape processing 3. for failover / failback between DLms during either a planned or unplanned event. GD Tape Monitoring As discussed in the DLm Overview section earlier in this white paper, a DLm solution is made up of a number of components. When DLm2100 is being used the solution may be as simple as 1 or 2 DLM2100s physically connected to a Data Domain storage controller, replicated to a remote Data Domain storage controller at another site. DLM8100, on the other hand has multiple hardware components making up the solution. Minimally there are two (2) 10 Gigabit Ethernet switches used to connect Virtual Tape Engines (s) to storage. There are two (2) 1 Gigabit Ethernet switches connecting the s in a control network allowing administration and control of the environment. There are 1 to 8 engines each with 2 FICON attachements and connections to the 10 Gig E switches, and there is 1 or 2 storage subsystems that may include multiple storage controllers / data movers. 7
Finally, there are replication links and services which are used to replicate data between DLMs in order to provide data protection to the overall two site environment. GD Tape software runs as a started task in a production zos LPAR on the mainframes making up the two site environment. GD Tape monitors the storage, s, switches, filesystems, and replication links to insure operation of the solution. GD Tape automatically alerts mainframe operations when a fault or error condition is detected in the DLm environment. Providing operations staff the opportunity to take whatever corrective action deemed necessary based on the alert that has been raised. Test Setup / Teardown DLm environments are typically made up of two DLms replicating data between each other in order to provide data protection. As shown in Figure 5, a typical two site DLm configuration has two copies of both DLMs libraries. The DLm at Site 2 has its own production DLm library (L2) as well as a backup copy of Site 1s library (L1B). Site 1 has its own production library (L1) as well as a copy of Site 2s library (L2B). Site 1 Site 2 Monitoring Monitoring L1 L2 L2B L1B Figure 5 A Typical 2 Site DLm Environment with GD Tape A single DLm library is typically made up of 1 to many filesystems. Each filesystem within a DLm library may contain hundreds or even thousands of individual tape volumes (VOLSERs) depending on the sizes of both the filesystems and the tape volumes residing in them. There are two critical requirements for conducting a test in a two site DLM environment: 1. Allow testing to occur with minimal or no disruption of production tape processing and data replication between sites. 2. Allow full destructive testing where individual tape volumes (VOLSERs) may be modified and scratched during test without have permanent impact to those volumes once the test has completed. GD Tape satisfies these two requirements by providing automated scripts to create a copy of a DLm library. Once GD Tape has built the copy (snapshot) of the DLm library, a DLM test library with indepent virtual drives can be stared on the DLM s and used to conduct a mainframe test without disrupting whatever production processing might be going on in the enviroment. Let s take a closer look at how Testing might be performed. 8
Referring to Figure 6, Site 1 is a production mainframe environment. The L1 library is a production library that must be maintained for production processing. For the sake of discussion let s assume the L1 tape library is made up of 10 individual filesystems, each of which may contain 100s or 1000s of virtual tape images (VOLSERs). Site 1 Monitoring Monitoring Site 2 Library Library L1 L2 L2B L1B L1dr Figure 6 DLm Test Environment All 10 of the filesystems making up the production tape library are being replicated to a DLm at site 2 and stored in a backup library (L1B). These filesystems are not normally configured as part of a virtual tape library at site 2. They are inactive filesystems only used as targets to the replication services running at Site 1. Using a GD Tape ISPF interface, a system administrator would instruct GD to snap the backup library. GD Tape automatically takes a snapshot of each of the 10 filesystems making up the backup and creates a copy (L1dr) for use during testing. Replication from site 1 to site 2 continues. The L1dr copy of the library takes very little incremental space on the DLM at Site 2. Snapshots are done by building pointers to the backup copy (L1) maintaining copies of data that is changed during the test. Once the library has been created, a test virtual tape library is defined across the DLm s and drives are varied online in the mainframe at site 2. Full read / write access to all tapes in the Test library are available during the test. Once testing is complete, the test library devices are varied offline. GD Tape can now be instructed to discard the snapshot of the library, deleting the snapshots of the 10 filesystems from the DLm. Full production processing has continued and been available throughout the Test. Replication between the product library at site 1 and the copy of the ibrary at site 2 has remained active implying that the library has been fully protected during the test. 9
Failover / Failback GD Tape constantly monitors the DLm solution and provides alerts to mainframe operations when a fault and/or critical condition is detected. GD Tape does not on its own initiate an automatic failover or swichover of a DLm library from one DLm to another. GD Tape simply notifies operations that an error has been detected. If DLm failover / switchover is deemed necessary, then mainframe operations can initiate GD Tape automation to conduct the failover / switchover. Once again refering to Figure 4. Assume that the production DLm at site 1 has experienced a critical failure. GD Tape has notified operations and it has been determined that a full failover of the DLM 1 library to DLM 2 is necessary in order to allow batch processing to be performed at Site 2 until such time that Site 1 can be restored. Assuming replication from DLm 1 to DLm 2 has been disrupted, GD Tape can be used at Site 2 to promote the copies of Site 1s filesystems (L1B) making them read/write capable. Once the filesystems are read/write ready the s on the DLm at Site 2 are updated to define a virtual tape library and drives to access the new library. Drives are then varied online and batch processing at Site 2 is available. Once Site 1 is restored, a failback process would be initiated to synchronize the filesystems from Site 1 with any changes that have occurred at Site 2 during the outage. Once all filesystems are up to date, the filesystems at Site 2 would once again be established as targets for the filesystems at Site 1 with processing at Site 1 and replication to Site 2 being resumed. Switchover / Switchback Some planned and unplanned outages are short enough that a full failover / failback may not be warranted. GD Tape allows processing at Site 2 with read-only access to tape volumes from Site 1 through a process referred to as Switchover. When operations initiates a switchover, GD Tape will make the target, backup copy (L1B) of the producion library available to a virtual library defined on the DLm at Site 2 in read-only mode. Any batch job requiring read-only access to a tape volume (VOLSER) normally located at Site 1 can be run at Site 2 and gain access to the needed VOLSER in the backup library (L1B). The advantage of establishing a switchover environment is that no failover is required to re-establish the DLm at Site 1. Since no tapes in L1B are updated during switchover processing, there is no need to re-sync data from L1B back to L1 before restarting the production DLm at Site 1. Instead the read-only library at Site 2 is idled and the production library at Site 1 is simply re-initiated. GD for Universal Data Consistency TM Dell EMC offers a unique data consistency solution for customers using both VMAX as their primary mainframe DASD and Disk Library for mainframe with VMAX backend storage for their virtual tape library. Dell EMC Mainframe-Enaber software includes Consistenty Group (ConGroup) and Multi-Session Consistency (MSC) software packages that run on an IBM zos mainframe to provide point in time data consistency across CKD devices and/or LUNs being replicated using Symmetrix Remote Data Facility (SRDF). ConGroup provides data consistency for synchronous replication links (SRDF/S) while MSC provides data consistency for asynchronous replication links (SRDF/A). Using the full GD product, 2-site and 3-site VMAX SRFD configurations, including 3-Site STAR, can guarantee that devices / LUNs defined in a single consistency group will be maintained in a single point in time insuring that restart at a site can always be performed. When DLm is configured with VMAX storage as the primary DLm Virtual Tape Library, GD supports DLm storage being included with VMAX storage into a single consistency group providing an industry unique Universal Data Consistency across both mainframe DASD and Tape. Figure 7 shows a fully implemented UDC configuration in a 3-Site STAR environment. In such an environment ConGroup software will insure that data stored in 3390 volumes on VMAX DASD will be maintained consistent with DLm virtual tape data stored in the fibre channel VMAX storage within the DLM virtual tape library where the data is being replicated from the top-left site in Figure 6 to the topright site in Figure 6 using SRDF/S. Likewise, MSC software will insure that data stored in the VMAX DASD storage will be maintained consistent with data in the DLm VMAX storage as data is Asynchronously replicated using SRDF/S to the site in the bottom of Figure 6. 10
GD software running on each of the mainframes will monitor the total environment and provide automatic alerts to any abnormality that may occur. Allowing operations to initiate whatever action may be necessary to keep the environment running smoothly. zseries VMAX DASD VMAX DASD zseries GD ConGroup ConGroup GD SRDF/S SRDF/ A VMAX DASD MSC Group GD zseries Figure 7 GD with Universal Data Consistency for VMAX DASD and DLm Summary Disk Library for mainframe is a tape-on-disk virtual tape library for IBM mainframe environments. Data protection and Disaster Recovery is provided by replicating the DLm library to a separate DLm at a remote location. GD Tape is optional software available to zos mainframe environments for assisting in the operation and management of two site DLm environments. GD Tape provides 3 types of services to the 2 Site DLn environment: 1. DLm Solution Monitoring with Automatic Alerting 2. Operations initiated Setup and Tear-Down of DLm Test Environments and Libraries. 3. Operations initiated planned and unplanned Failover and Failback of the DLm solution. Using GD Tape, DLm users can easily and efficiently manage their DLm operations. GD Tape is available to DLm customers in zos environments when using either VNX and/or Data Domain storage as their primary DLm repository. GD Tape was derived from GD which focuses on provide automated Disaster Recovery and Restart for mainframes using VMAX storage as their primary mainframe DASD. Additionally, GD provides an industry unique Universal Data Consistency solution for customers using both VMAX DASD and DLm with VMAX storage as their primary DLm data respository. For these customers, GD UDC insures a until point-in-time data consistency across both mainframe CKD DASD volumes and the DLm virtual tape library. 11