I can't speak to all (most?) of the current architecture boxes, but to attempt to answer Jantje's question, yes the boxes I'm familiar with will definitely store less data on small block sizes. I am not speaking of the boxes that do thin provisioning because I haven't used this feature, but on IBM DS6800, EMC Symm (VMAX and DX4 w/o thin provisioning), and older HP/Hitachi XP arrays, when the physical disk was carved up into logical volumes for the emulated 3390 on top of them, storage was reserved for the physical capacity of the emulated drives. Thus if I carved up physical disk into 3390-9 volumes, the array would reserve 8.3 GB of physical space per 3390-9 volume.
Rex ________________________________________ From: IBM Mainframe Discussion List [IBM-MAIN@LISTSERV.UA.EDU] on behalf of Eric Bielefeld [eric-ibmm...@wi.rr.com] Sent: Tuesday, July 23, 2013 12:20 PM To: IBM-MAIN@LISTSERV.UA.EDU Subject: Re: BLKSIZE=3120 I believe that the net result of coding smaller blocksizes does result in being able to store less data. If you had 1,000 volumes all defined as 3390-9s, and each volume had 100 datasets that filled the volume blocked at 512 bytes, you would store a fraction of the data if you blocked each of those datasets at 1/2 track blocking. That is a function of the z/OS archictecture. I don't know exactly how the data is stored on the tracks, but I believe that the result of smaller blocksizes means that you will store a lot less data. Ron Hawkins probably is the best definitive source on this subject. Eric Bielefeld Retired z/OS Systems Programmer Milwaukee, Wisconsin 414-475-7434 ----- Original Message ----- From: "Jantje." <jan.moeyers...@gfi.be> Newsgroups: bit.listserv.ibm-main To: <IBM-MAIN@LISTSERV.UA.EDU> Sent: Tuesday, July 23, 2013 5:32 AM Subject: Re: BLKSIZE=3120 Taking the risk of starting another flame war here... Are there still any shops that have actual SLED? In today's world of emulated DASD, would it really still hold true that using smaller block sizes is actually wasting space? After all, these bytes are in the end physically written to FBA devices with 512 byte sectors, no? In the old days, there were inter-record gaps that took up space, but is this still the case? And even if the emulation is so good that it simulates those, what is happening with the actual capacity of the physical disks. Is that being eaten by simulated IRG? Thanks for shedding some light on this, whoever knows the internals of these current DASD boxes, Jantje. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN The information contained in this e-mail may contain confidential and/or privileged information and is intended for the sole use of the intended recipient. If you are not the intended recipient, you are hereby notified that any unauthorized use, disclosure, distribution or copying of this communication is strictly prohibited and that you will be held responsible for any such unauthorized activity, including liability for any resulting damages. As appropriate, such incident(s) may also be reported to law enforcement. If you received this e-mail in error, please reply to sender and destroy or delete the message and any attachments. Thank you. NOTICE: This e-mail message, including any attachments and appended messages, is for the sole use of the intended recipients and may contain confidential and legally privileged information. If you are not the intended recipient, any review, dissemination, distribution, copying, storage or other use of all or any portion of this message is strictly prohibited. If you received this message in error, please immediately notify the sender by reply e-mail and delete this message in its entirety. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
