[email protected] (Rick Fochtman) writes: > My 2 cents worth: the "cheap DASD" doesn't live up to the reliability > standards that IBM demands for z/OS. Stop and think, really hard, > about the demands on z/OS DASD storage, as opposed to the "standards" > you enjoy with your PC DASD. How many of your PC's stay up, with DASD > spinning, on a 24/7 basis, for several years without problems?
commodity priced disks drove MTBF past 800,000 hrs, in part because of service & return costs would eliminate slim margins. nearly all hardware is now nearly identical ... differentiation is some electronics ... and RAS coming from various replication and RAID technologies. All current DASD is CKD emulation on top underlying fixed block disk hardware ... that is close to same across industry. I've paid more for things like replicated power supplies and hot-pluggable ... but that was the frame ... there was essentially no difference in the underlying disk hardware. By the mid-80s ... large variety of platforms were moving past hardware as major contributor to outages ... it was software, human error ... and environmental ... when we were out marketing our HA/CMP product I coined the terms "geographic survivability" and "disaster survivability" to differentiate from disaster/recovery. When I was asked to write a section in the corporate strategic continuous availability document the section was pulled because of complaints from both Rochester and POK (about not being able to meet the criteria at the time). misc. past posts mentioning availability (and/or corporate continuous availability strategy document) http://www.garlic.com/~lynn/submain.html#available and our ha/cmp product http://www.garlic.com/~lynn/subtopic.html#hacmp old foils/pitch of Jim's from '84 on availability (and stats on what was causing outages): http://www.garlic.com/~lynn/grayft84.pdf old posts mentioning CKD dasd, multi-track searches and FBA (including being told I had to show business case to justify $26M cost for MVS documents & education ... even if I provided MVS fully integrated and tested FBA support) http://www.garlic.com/~lynn/submain.html#dasd old posts mentioning getting to play disk engineer in bldgs. 14 & 15 http://www.garlic.com/~lynn/subtopic.html#disk -- virtualization experience starting Jan1968, online at home since Mar1970 ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
