tony.j.new...@btinternet.com writes: > This happend to us, 3380 continued to write x'00' over VM byte > allocation map on cyl 0.
Original CMS filesystem from the mid-60s almost had a fix for this ... updated filesysem control information was written to new locations ... and then the MFD was rewritten pointing to the new version of control information rather than old version. It worked for all writes except for the MFD. The new CMS "EDF" filesystem in the 2nd half of the 70s went to a pair of MFDs. There was the current MFD and a write would always be to the alternate MFD ... if completely corectly, the alternate becomes the (new) current and the (old) current becomes the alternate. A version number goes at the end of (EDF) MFD, on startup/recovery, both MFD is read and the most recent one is used ... a power failure, trailing zeros write would always result in that record appearing as older than the other MFD. In early 80s, I did a CP kernel filesystem ... including spool file system that addressed the problem for CP also. My motivation was that I had HSDT project and I needed VM370 spool file system that ran much faster for RSCS driving multiple T1 (& faster) links (standard spool file system typically got 5-32kbytes/sec ... I needed 3mbytes or better throughput. some past posts http://www.garlic.com/~lynn/subnetwork.html#hsdt I did the implementation in vs/pascal running in virtual address space but still managed to significant improvement over the standard implementation done as part of vm370 kernel in assembler. At one point, I thought I finally had a path to getting it picked up through the corporate network backbone which nodes were moving to multiple 56kbit links. However, this was about the time the communication group was putting intense pressure on the corporate nework to move to SNA ... technical people started being excluded from the backbone meetings ... so they could focus on the pressure being applied to move to SNA. However, by that time I also was doing the throughput enhancements to mainframe TCP/IP product (also implemented in vs/pascal). At the time, the standard product got about 44kbytes/sec using nearly full 3090 processor. In some tuning tests of the "fixes" at Cray Research between Cray and 4341 ... got channel speed throughput using only modest amount of the 4341 processor (possibly 500 times improvement in bytes moved per instruction executed). some past posts http://www.garlic.com/~lynn/subnetwork.html#1044 old email reference to communication group forcing internal network to move to SNA: http://www.garlic.com/~lynn/2006w.html#email870302 and http://www.garlic.com/~lynn/2011.html#email870306 other trivia ... I had also done a paged-mapped CMS filesystem originallyh for CP67 ... and then later moved to VM370. In the early 80s (on 3380 drives), side-by-side comparison of moderate i/o intensive workload ... it would get three times the througput of standard CMS filesystem. some past posts http://www.garlic.com/~lynn/submain.html#mmap old post with some (mmap) benchmark measurements from the 1st half of the 80s ... included in '86 SEAS presentation http://www.garlic.com/~lynn/2006.html#25 DCSS as SWAP disk for z/Linux and repeated in hillgang meeting http://www.garlic.com/~lynn/2011c.html#88 Hillgang -- VM Performance -- 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
