That leads to a question that I've been thinking about for some time. Since the 3390 geometry is emulated by modern storage control units, why then are the inefficiencies of small blocks emulated also? There are not SLEDs actually storing the data, why are IBG's, sectors, and all the other CKD nastiness emulated that makes 80 byte blocks such a bad idea? IOW, why can't the control unit simply store 708 * 80 byte blocks on a 56,664 byte 3390 track? Does zos's calculations take these inefficiencies into account and only write 78 of these blocks per track?
Inquiring minds want to know Dana On Tue, 7 Feb 2012 16:28:33 +0100, R.S. <[email protected]> wrote: >RAID has very little to do with half-track blocks. > >Nowadays 3390's are emulated, usually on RAID protected disk arrays (*), >but the 3390 geometry remains unchanged from z/OS point of view. >So half-track blocks (**) are still the most effective in terms of >storage utilisation and performance. > ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
