IBM Systems Magazine, Mainframe Edition - May/June 2013 - (Page 42)

Administrator Getting the most from your systems z/VM SSI Gains Traction Single system image feature delivers greater flexibility and resilience By Romney White ince its introduction in 2011 with z/VM* 6.2, client adoption of the single system image (SSI) feature has been growing. By enabling clustering of up to four z/VM systems and introducing mobility for VMs within a cluster, SSI has brought new flexibility and resilience to address some long-standing customer requirements. S While often regarded as a monolithic capability, SSI comprises several distinct technologies that together present the appearance of a single system. Figure 1 (page 44) shows the structure of a typical SSI configuration. Its major components are: Communication—The foundation is a dedicated network and an exploiting software infrastructure that enables communication between z/VM hypervisors. This mechanism—coupled with multisystem synchronization and well-defined cluster state management—enables many of the other SSI capabilities. Shared user directory— The z/VM user directory holds the definitions of all VMs and their configurations. In an SSI environment, a single user directory allows a VM to be known to and activated on any member in the cluster. SSI prevents a guest from being simultaneously active on more than one member. 42 pg 42-45.indd 2 MAY/JUNE 2 013 Shared spool files—Spool files are used in z/VM to virtualize unit record devices—card readers and punches, printers, etc.—and hold VM console device log files. Regardless of which member is hosting a VM, its spool files are made available to it by sharing them throughout the cluster. Minidisk protection— A minidisk is a contiguous area on a physical disk that can be associated with a VM as a virtual disk device. Minidisks can be shared with other VMs and access to them is established based on a set of rules and the nature of the sharing. For example, access to a minidisk may be requested as readonly, and the request can be made conditional upon whether another VM has read/write access to it. In the SSI environment, these rules are enforced across the cluster, ensuring data integrity is maintained. Shared networks—In addition to the private hypervisor communication network, customer Ethernet networks are used to enable commu- 4/16/13 9:15 AM

Table of Contents for the Digital Edition of IBM Systems Magazine, Mainframe Edition - May/June 2013

IBM Systems Magazine, Mainframe Edition - May/June 2013
Table of Contents
Editor's Desk: See Beyond the Silos
IBM Perspective: Keys to Successful Software Development
Dashboard: It's a Smarter World After All; Encouraging Exercise; Facebook Fatigue?
Insider: Reimagining Data Protection Requires Due Diligence and Defense in Depth
Case Study: Financing the Future: BNY Mellon increases workload and cuts costs by investing in a standardized mainframe environment
Feature: Making DevOps Real for System z: Linking development and operations for the continuous delivery of software innovation
Feature: Building a DevOps Pipeline: Automated testing to support application development reaps many rewards
Tech Corner: Software-Defined IT Infrastructure: The Next Chapter in Virtualization Benefits
Administrator: Single System Image Feature Delivers Greater Flexibility and Resilience
Solutions: CA Mainframe Application Tuner; Ivory Hub; Genius Project; CICS JS/Server; CA Workload Automation; QWS3270 Tablet
Advertisers Index
Stop Run: Un-Comfort Zone
Reference Point - Global Events, Education, Resources for Mainframe
Services Blueprint Issue 1 2013
2013 Mainframe Buyer's Guide Index

IBM Systems Magazine, Mainframe Edition - May/June 2013