On Wednesday, 10/21/2009 at 12:36 EDT, Alain Benveniste <a.benveni...@free.fr> wrote: > I'm not sure what should be understood by "Single System Image" ? > Could you give me a brief explanation of this meaning ?
A Single System Image will be a cluster of 2, 3, or 4 z/VM LPARs that has the following characteristics: a) All member systems are in an ISFC collection created by FICON CTC connections b) All members are connected to the same SANs and Ethernet LAN segments, with the same access rights c) They share dasd volumes. d) With special exceptions, the users have identical directory entries on each system e) The users all have the same "security context". That is, users have the same privileges and access rights without regard to which of the member systems they log onto. Attributes of the cluster include: 1) System programmer-defined cluster configuration (the systems can share a single SYSTEM CONFIG) 2) Except for those above-mentioned special exceptions, a user can logon to only one member of the cluster at a time 3) Subject to those same exceptions, users can access their spool files from any member of the cluster, regardless of which system they were logged onto when they created them. (The cluster member must be up in order to see spool files created on that member.) 4) Class G users will generally experience a single image. I.e. QUERY NAMES shows the users from all of the systems. TELL ALAN works without regard to the system ALAN is logged on to. SET SECUSER doesn't care where in the cluster either user is located. 5) There are cross-system LINK protections (similar to XLINK-protected disks) 6) The ability to maintain (SERVICE) all of the member systems from a single system. 7) The capability to move most running Linux guests from one member to another without having to hibernate it or shut it down 8) Built-in data and virtual server integrity protections during guest relocation 9) Other cool stuff Except for item 7, people may recognize this as being similar to Cross System Extensions. It's true that CSE provided inspiration, but unlike CSE, a single system image (SSI) cluster is managed by CP himself and has more capabilities than CSE. Note that the above are a Statement of Direction. "Such statements are subject to change or withdrawal without notice and represent goals and objectives only." Alan Altmark z/VM Development IBM Endicott
