jcal...@narsil.org (Jerry Callen) writes: > In another thread, l...@garlic.com wrote: > > ... but then if MVS had FBA support wouldn't have needed to do 3380 > as CKD (even tho inherently it was FBA underneath) ... > > I didn't know that. > > Was that the first (and/or last?) IBM SLED to be inherently FBA under > the hood? Where were the smarts for that implemented, in the control > unit, or the drive itself?
re: http://www.garlic.com/~lynn/2015f.html#86 Formal definituion of Speed Matching Buffer hardware speed and error correction was going to fixed-sized blocks. You can see this in 3380 track capacity calculations where record sizes have to be rounded up, sort of compromise hack given that MVS wasn't going to support real FBA. The 3380 was smaller fixed-sized blocks ... but not "true" IBM FBA like 3310 & 3370. 3375 was the first CKD emulated on top of an IBM FBA (3370) device. 512-byte blocks have prevailed for a couple decades (IBM 3310 & 3370 and follow-ons ... but also all the other industry standard disks). There is currently inudstry move to 4096-byte fixed blocks for improved error correction and track capacity. https://en.wikipedia.org/wiki/Advanced_Format http://www.seagate.com/tech-insights/advanced-format-4k-sector-hard-drives-master-ti/ eckd originally for speed-matching buffer ... was also trying to retrofit a little of the FBA benefits to CKD architecture (again because MVS wouldn't upgrade to real FBA). part of the issue for 3375 was there wasn't a mid-size CKD disk (just the high-end 3380). Large customers were buying hundreds (& thousands) of vm/4300s for distributed non-datacenter market (sort of leading edge of the coming distributed computing tsunami; for instanceNATO got 6000 vm/4341s) ... and MVS couldn't play in that new market with no mid-range CKD disk. Doing the 3375 CKD at least gave MVS a path ... however MVS support was really oriented around having 10-20 people in large datacenter. The idea of supporting a thousand distributed systems out in departmental areas wasn't very practical. I also got dragged into doing benchmarks for LLNL that was looking at 70 4341s for computer farm (sort of leading edge of the future supercomputing paradigm). 4341 was faster than 158&3031 ... and clusters of 4341s were faster than 3033, lower aggregate cost, lower aggregate physical and environmental footprint, also higher aggregate memory and i/o throughput. old email http://www.garlic.com/~lynn/lhwemail.html#4341 past posts http://www.garlic.com/~lynn/submain.html#dasd -- virtualization experience starting Jan1968, online at home since Mar1970 ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
