That reminds me of an incident in my first ever job on a 360/25 They had three 3211 disk drives and were running a large tape to tape sort with work files spread across two of the disks. In the middle of the sort a disk had a hardware check. Engineer came, reset the disk but no fault was found. Re-started the machine and ran the job again. At the exact same point in the job the disk checked again. Engineer came back and watched as the job ran - the heads on the two drives were seeking back and forth so much that both drive units were rocking slightly and at the critical point the two boxes clashed and bingo. The solution was to move the drives quarter of an inch further apart.
Ray Pearce -----Original Message----- From: IBM Mainframe Discussion List [mailto:IBM-MAIN@LISTSERV.UA.EDU] On Behalf Of Seymour J Metz Sent: 23 July 2019 17:35 To: IBM-MAIN@LISTSERV.UA.EDU Subject: Re: DASD nostalgia Nothing as drastic as the alleged FastRand, but I can vouch for 3330 and 3330-equivalent drives dancing. My boss told me to write a program that started at the middle of the pack and then did seeks in and out to the first untouched cylinder until it had hit every cylinder. I told him that the timings from the test would have no relevance to performance in the wild, but he insisted that I write it anyway. -- Shmuel (Seymour J.) Metz http://mason.gmu.edu/~smetz3 -- This e-mail message has been scanned and cleared by Google Message Security and the UNICOM Global security systems. This message is for the named person's use only. If you receive this message in error, please delete it and notify the sender. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
