There is a lot of confusion about 'dasdfmt' versus 'mkfs'. If you already know the difference, please excuse this note. The water is muddier for mainframers because in z/OS land the concept of "filesystem" and "volume" is blurred. z/OS uses the low level structure (tracks, blocks, records, even counts and keys) where most other op sys do not. CMS does not and even CP can live without it. VSE is happy there too, which is probably why VSE and CP and CMS (and Linux and AIX and Solaris) are all content to run on FBA. z/OS has an allergy to fixed block storage and requires CKD.
CKD on Linux must be formatted both low level (dasdfmt) and high level (mkfs, usu also fdasd). FBA on Linux needs no low level formatting. Go directly to 'mkfs'. Do not pass "go"; do not collect $200. (but see below) CKD on CMS must be formatted both "low level" and "high level". The CMS FORMAT command handles both (for CMS minidisks). It blocks the disk (these days usually 4K) and then creates and empty CMS "EDF" filesystem. A disk which has been formatted with CMS FORMAT can be used by Linux without 'dasdfmt'. I will skip discussion of ICKDSF and CPFMTXA for this context. FBA on CMS does not require low level formatting, so CMS FORMAT silently skips that part and proceeds immediately to lay down the EDF filesystem we all know and love. By default, it writes zeros, but you can opt out of that and get instant completion. Logical blocksize can be 512, 1K, 2K or 4K, but the physical blocksize is always 512. In a word, RESERVE. If you will be using partitions (don't get me started!) then I recommend doing a CMS RESERVE. This works for CKD or FBA. The result is that /dev/dasdy1 will map byte-for-byte with the reserved file. I hope this helps. -- R; <>< Rick Troth Velocity Software http://www.velocitysoftware.com/ ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 ---------------------------------------------------------------------- For more information on Linux on System z, visit http://wiki.linuxvm.org/
