A somewhat broader search found the 1984 RT-11 System Release Notes with the following: 1.4.2.4 Logical Disk Subsetting Handler (LD) - The logical disk subsetting handler lets you define logical disks, which are subsets of physical disks. You define logical disks by assigning a logical disk unit number to a file on a physical disk. You can then use the logical disk as though it were a physical disk. AA-5286F-TC-T1_RT-11_System_Release_Notes_Jul84.pdf (bitsavers.org) <http://www.bitsavers.org/pdf/dec/pdp11/rt11/v5.1_Jul84/AA-5286F-TC-T1_RT-11_System_Release_Notes_Jul84.pdf> p15/102 Suggests DEC had not yet adopted the term ?partition? for a segment of a disk Tom -----Original Message----- From: Tom Gardner [mailto:tom94022 at comcast.net] FWIW a Google search: "partition site:http://www.bitsavers.org/pdf/dec/pdp11/rt11" returns no relevant hits prior to 1983 I suspect that ESDI and MFM controllers emulating RL/RK disks are also later than 1983 Tom -----Original Message----- From: Zane Healy [ <mailto:healyzh at avanthar.com> mailto:healyzh at avanthar.com] Sent: Monday, January 31, 2022 12:40 PM To: Paul Koning; General Discussion: On-Topic and Off-Topic Posts Cc: <mailto:t.gardner at computer.org> t.gardner at computer.org; Tom Gardner Subject: Re: Origin of "partition" in storage devices On Jan 31, 2022, at 11:28 AM, Paul Koning via cctalk < <mailto:cctalk at classiccmp.org> cctalk at classiccmp.org> wrote: Partitions are pretty important in RT-11 v5.x, after all, there is the partition size limit, so you have to have multiple partitions for almost any HD, except very small ones. Let?s not forget hardware enforced partitioning, the WEQSD/04 ESDI controller comes to mind. It see?s a single large ESDI HD as a single disk, but you can partition it on the controller, and the OS sees each partition as a separate physical disk. I seem to remember some MFM controllers that made the MFM drive appear to be RL01/RL02 or RK05 packs. Zane