IBM Systems Magazine, Mainframe Edition - January/February 2012 - (Page 36)

Tips and Techniques Tactical solutions Virtualization Reshapes How Data is Stored Where, physically, is your data set? That’s a difficult question to answer recently heard a report on how technology will change in the next 25 years. If the predictions are accurate, we’ll see some incredible advancements. Over the past 30 years of my career, I’ve already seen extraordinary change. One of my first jobs in the industry was working on an IBM 4381 system with IBM 3330 and 3350 disks, as well as old-fashioned tape. For professionals entering the field today, this environment would be incomprehensible. The 4381 could be configured with up to 32 MB of processor storage, and one 3330 device could hold 200 MB of data. Manually mounted tapes were not automated and had no robotics. The capacity was far from today’s cartridge capacity of 4 TB for manual tapes. Physically mounting 3330 disks was a workout in itself. With this older technology, there was: relaxed stance when allocating data sets on volumes. Understanding disk and tape virtualization is key to efficiently managing data sets. Advances in disk technology have resulted in two key benefits: Less floor space is required, and the physical capacity of devices has increased. The DS8800*, for example, has a small footprint, but one disk controller and a few attached frames can hold 1,024 TB of data. Newer disk technology is so sophisticated that several fault-tolerant processors are delivered in the disk box itself. By John Iczkovits I hÁLittle or no automation, so you needed to know much more about the system hÁAlmost no virtualization, so you could actually see, feel and hold data As a result, most people still view volumes as physical, and many still take painstaking care to place their data sets both for performance and to avoid space-related problems. However, you can now take a more A Turning Point In 1997, IBM disk technology changed dramatically with the introduction of the RAMAC virtual array (RVA). Instead of writing to one physical disk, data was virtualized onto an array of disks. Although the RVA, Shark and DS8000 work very differently, they all use virtual arrays and not an individual physical disk. With modern disks came a new way of dealing with data-loss mitigation in the form of RAID. Several levels of RAID are available, with the vast majority of mainframe customers using RAID 5, 6 or 10. Along with RAID, the physical disk is further broken down to arrays and then ranks, which contain a set of eight physical disks picked by the controller. Reading or writing a logical disk no longer uses one specific physical volume, as was the case prior to using disk arrays. Rather, the data is hardwaresingle-striped across all or a subset of eight devices by default, depending on the RAID technology chosen. Three types of disk devices exist: hard disk drive (HDD), serial ATA and solid-state drive (SSD). Each individual disk is called a disk drive module (DDM). The vast majority of devices used are HDDs, which are sold in different sizes and at different speed rotations. For example, one option for the DS8800 is a 2.5-inch SAS drive with a capacity of 600 GB at 10,000 RPM. An array or rank is eight of the same devices. To build the 1,024 TB capacity for a DS8000 requires about 1,000 disks in the control unit, plus attached frames. Architecturally Speaking From an architectural point of view, allocations are based on 3390 emulated devices. The most common 3390 emulated devices are models 1, 2, 3, 9, 27, 54, and A, which is an extended address volume (EAV) device. Models 27 and 54 are known as mod 9 devices and have larger capacity. These emulated logical volumes are single-striped across the rank. 22 36 JANUARY/FEBRUARY 2 012

Table of Contents for the Digital Edition of IBM Systems Magazine, Mainframe Edition - January/February 2012

IBM Systems Magazine, Mainframe Edition - January/February 2012
Table of Contents
Editor’s Desk: Simplicity Itself
IBM Perspective: The Changing Data Center
Insider: Solve the DevOps Challenge With Orchestrated IT
Q&A: Guru Rao Explains How a Better World Begins With Smarter Computing
Case Study: A Comfortable Place: Furniture Brands rests easier with SecureAgent's backup and recovery solution
Cover Story: Smarter By Design: "That's the way to build capacity and hold costs flat," says IBM VP Doug Brown
Feature: Another Dimension: What sets the zEnterprise environment apart?
Tech Corner: How You Do What You Do When You're a z196 CPU
Tips & Techniques: Virtualization Reshapes How Data Is Stored
Solutions: CA Mainframe Application Turner - M4Workbench Eclipse - Virtual Machine Backup
Resources: Advertisers’ Index
Stop Run: Through Three Generations, One Family's Story Shows That While Technology Has Changed, IBM's Fundamental Mission Hasn't
Reference Point - Global events, Education, Resources of Mainframe

IBM Systems Magazine, Mainframe Edition - January/February 2012