On Nov 30, 2007 4:34 PM, Mike Walter <[EMAIL PROTECTED]> wrote: > I've never understood why Linux needs CMS to format the MDISK before Linux > formats it. What a waste of I/O's (even if z _does_ perform I/O VERY, VERY > quickly!). What a waste of time, and what a set of cludgy processes.
:anecdote. Long, long ago... there was a bug in the Linux dasdfmt that caused it to miss some tracks while formatting the disk (causing errors when using the disk). The difference with a CMS formatted disk is just in the first tracks so we ended up doing CMS FORMAT (actually, the RVA let us flashcopy from a common prepared CMS disk and tweak it) followed by a Linux dasdfmt for only 1 cylinder. Even when the bug was fixed, we still used this because it saved us a lot of time in preparing new disks. Some VM storage folks knew that for user packs you only have for format cylinder one, so they picked up that habit... Then folks in Boeblingen got upset because other people did dasdfmt for 1 cylinder without CMS FORMAT first, and called support... so the option to format part of the disk was removed. The silly errors for unformatted disks showed up in one of the early versions of the eckd driver. I specifically recall educating the developer on using READ TRACK for reading the volser. That got fixed, but after a rewrite of the driver it was broken again. Open Source means someone else may fix that now... And the other reason for CMS FORMAT (and RESERVE) is when you plan *not* to use dadfmt but use the diagnose driver. That's RESERVE is strange artifact as well, but that's another story. Rob Rob
