IBM Systems Magazine, Mainframe Edition - March/April 2010 - (Page 46)

Administrator Getting the most from your systems Effective Virtualization Implementation DCSS technology improves Linux performance and upgrade management By Steve Wilkins /VM* version 5 release 4 (V5.4), and later offers potential performance gains by building and cloning Novell SUSE Linux* Enterprise Server 11 (SLES 11) root filesystem images using System z* Discontiguous Saved Segment (DCSS) technology. Performance gains may be seen in the reduction of real main memory and CPU utilization, as well as in the reduction of virtual and real I/O. In addition to possible performance gains, simplification of rolling out changes and upgrades to Linux images is also possible with DCSS technology. A more detailed performance analysis is available online ( DCSS Technology DCSS is z/VM vitualization technology that allows ranges of virtual machine memory to be saved. This saved memory can then be loaded and shared among multiple virtual machines. Portions of that memory can also be defined as Read/Write (R/W)—allowing each virtual machine to maintain its own copy of that memory portion. This z/VM technology can be combined with Linux eXecute-In-Place (XIP) technology to build, share and use Linux file systems that greatly reduce real file system I/O and the real memory necessary to host Linux virtual machines running similar workloads. Prior to z/VM V5.4, a DCSS resided within the first 2 GB of real storage and couldn’t be larger than 2 GB. With the updated release, a DCSS can now reside above 2 GB. A single DCSS can still only be 2 GB in size, but V5.4 allows for the stacking of multiple DCSSs. With corresponding support in the Linux DCSS block device driver (dcssblk), very large DCSS-backed file systems can now be created. In addition, SLES 11 now fully supports DCSS technology. Editor’s note: This article is based on the IBM whitepaper “Sharing and Maintaining SLES 11 Linux under z/VM using DCSS and an NSS,” by Michael MacIsaac. The entire whitepaper can be found online ( Virtual Machine Setup Four main z/VM virtual machines can be used for cloning Linux images. For more information on the setup and MARCH/APRIL 2010

Table of Contents for the Digital Edition of IBM Systems Magazine, Mainframe Edition - March/April 2010

IBM Systems Magazine, Mainframe Edition - March/April 2010
Table of Contents
Editor's Desk: More Than a Milestone
Dashboard: A Text Can Save a Life
Data Display: Transistors: Tiny, Mighty Drivers of Innovation
Insider: Three Tips for Optimizing IT Investments
IT Today: IBM Cognos Now! Improves Linux on System z Business Analytics
Focus on Storage: XE for Storage on z/OS Version 4.2 Introduces Enhanced Functionality
Case Study: Implementing an IBM System z10 Enterprise Linux Server Helps EFiS EDI Finance Service AG Save Money and The Environment
Cover Story: After a Decade, Linux on System z Still has Merit
Feature: IBM Encourages Easy ISV Application Porting To Linux on System z
Administrator: DCSS Technology Improves Linux Performance and Upgrade Management
Tips & Technniques: Using System z Can Help Optimize Both Internal and External Communications
Advertisers' Index
Stop Run: IBM's Hursley House Encourages Innovation

IBM Systems Magazine, Mainframe Edition - March/April 2010