Talk:History of IBM magnetic disk drives

Missing disk drives - 7303 and 3344

The article is missing information on the 7303 and 3344 drives.

The 7303 is problematical because of the scarcity of documentation, as discussed in #Disk drives on IBM 7030 (Stretch) - 353 versus 7303?. I'm not sure what, if anything, should go into the article.

The 3344 came out at about the same time as the 3340 and 3350. All of the 3344 models are B units and require a 3340-A2 head of string; for that reason perhaps they should be in the 3340 section rather than a section of their own. 05:03, 31 May 2021 (UTC) Shmuel (Seymour J.) Metz Username:Chatul (talk)

I doubt if either is controversial, so why don't you go ahead and add them? unsigned 18:11 31 May 2021 User:Tom94022

What I know about them is limited to the information in an early Stretch manual and in the 3340/3344 manual. If you want I can add information based on those, but it won't have the level of detail present for some other devices. Shmuel (Seymour J.) Metz Username:Chatul (talk) 19:07, 1 June 2021 (UTC)

I would go ahead with the 3444 as a sub-section to the 3340 much like the 3333 and the flavors of 2314. It was a 3350 but I don't know if there is an RS for that.

I'd completely forgotten about the 7303 issue, thanks for reminding me. I now found an RS (not online) which allowing for ECC gives the 353 the identical capacity as the 7303 so it is more likely they are same with different type numbers. I've also pinged an IBM alumni group to see if they can further clarify the situation. Why don't you hold off on the 7303 and when I gather some more information I will post it as appropriate. Tom94022 (talk) 22:27, 1 June 2021 (UTC)

@Chatul:How about I rename the section to Stretch disk drive and then list both numbers in the section along with common characteristics? Tom94022 (talk) 20:46, 2 June 2021 (UTC)

I'd make it Stretch disk drives, reference the 353, 354, 7303 and 7612, and mention that none of the sources give the relation between the 353 and the 7303. Shmuel (Seymour J.) Metz Username:Chatul (talk) 21:12, 2 June 2021 (UTC)

Stretch disk file using the code name that it developed under at IBM SJ as the section heading and only covering the "353 Disk Storage" and "7303 Disk Storage" might make sense. Tom94022 (talk) 20:56, 3 June 2021 (UTC)

Singular if the 353 and 7303 are the same, otherwise plural. Either way the text should mention what they attach to, the 354 and 7612. Shmuel (Seymour J.) Metz Username:Chatul (talk) 00:49, 4 June 2021 (UTC)

No, the 3344 was not a 3350; both the track size and the capacity of a volume are less.

Yes, since it attaches to a 3340A2 that determines the track size as a 3340 track and that is why the track size and capacity are lower. But I am pretty sure that under the skins it is the same as a 3350. Not sure I can find an RS for it but that is my recollection from working on them. Tom94022 (talk) 18:22, 3 June 2021 (UTC)

I've split the 3340 section into a 3340 subsection and a 3344 subsection; it's missing a lot of detail on the 3344. Shmuel (Seymour J.) Metz Username:Chatul (talk) 15:34, 3 June 2021 (UTC)

Missing disk drives - 7303

One possibility is that IBM split the 7303 into two boxes, a 354 controller and a 353 drive. The cited page for the 7303 mentions the same 7612 disk exchange but doesn't mention a controller between the exchange and the 7303. Maybe your contacts can confirm or refute that guess. Shmuel (Seymour J.) Metz Username:Chatul (talk) 21:12, 2 June 2021 (UTC)

Definitely a possibility in that it is consistent with the language in DISC FILE APPLICATIONS but that might not be enuf to make our conclusion not OR. Tom94022 (talk) 20:56, 3 June 2021 (UTC)

The 7030 Reference manual makes it clear that disk storage units connect to it. Other documents identify the only units to attach to the disk synchronizer are the 7303 and the 354 with a 353 and that as far as storage parameters go, the 353 and 7303 are identical. I think this gets us as far as the 7303 is equivalent to a 354 with attached 353. Comment? Tom94022 (talk) 23:47, 5 June 2021 (UTC)

@Chatul: The 1963 7030 Physical Planning Manual shows one 354 adjacent to to the 7612 and a remote 353 (sheets 14, 15 & 30/60). It does not mention the 7303. We know the 7612 can attach up to 32 disk storage units. Apparently the first one is a 353 and the remainder are 7303s. Since the 353 cannot connect to the 7612 further supports the conclusion that a 7303 was a 354 + 353 much like the 2414 DASF was a 2314 SCU plus 2x 2313 plus a 2312. Agree? It is certainly research but I don't think it quite rises to OR - comment? Tom94022 (talk) 00:19, 9 June 2021 (UTC)

I'd say mention that both 354/353 and 7303 attach to a 7612, mention the identical characteristics and include a hatnote that we don't know the connection between the 7303 and the 354/353.

Please correct 7020 in your citation. |id=, |section= and |section-url= would also be nice. I'd do it myself but changing someone else's talk text is frowned upon here. You can get a URL (subject to browser) to a specific page by appending #page=foo. The value of foo should be the PDF page number, which might not match the printed page number. E.g., something like this. --Shmuel (Seymour J.) Metz Username:Chatul (talk) 14:44, 9 June 2021 (UTC)

Chatul Check out this BYU 7303 in action! Historically this was likely the disk storage shipped to Mitre. It is pretty clearly a 353 if you compare the 353 manuals to this video. The mystery continues albeit now with hardware included. Tom94022 (talk) 17:03, 31 August 2021 (UTC)

References

Multiple requesting

The discussion of multiple exposure devices in Talk:Direct-access storage device#Remapping versus simulation of geometry has been intermixed with discussion of other issues, so I believe that it would lend clarity to move it to a separate section. The IBM 2305 Fixed Head Storage Module and IBM 2835 Storage Control introduced a new feature:

MULTIPLE REQUESTING

The multiple requesting function provides the capability for record request queuing within the 2835/2305 facility. This queuing is accomplished by allowing multiple set sector commands to be issued to a single disk module. The function is implemented by associating up to eight logical (system) device addresses with a single physical module. This permits the channel to issue a set sector command to one logical device, disconnect on channel end status, and then issue a set sector command to another logical device. The arguments transferred by the set sector command are stored in the control unit. Whenever the control unit is not executing a command and is not otherwise busy, it monitors the angular position counters in the attached disk modules. When a· counter compares equal with one of the stored arguments for that module, the control unit raises request-in and, when polled, presents device end status for the appropriate logical device.

To properly complete a chain when the channel reconnects, the control unit must store the arguments of set file mask and seek commands issued previously in the same chain. If mUltiple requests are pending against a module, the proper head may no longer be selected when the channel reconnects to complete the chain. If this is the case, the control unit ensures that the proper head is reselected prior to raising request-in.

this required that the 2835/2305 be connected to the new 2880 block multiplexor channel. Each of the logical addresses is known as an exposure.

In 1982, IBM reintroduced the concept with the 3880-11 and 3880-13; the later models 21 and 23 also supported multiple requesting.

With the announcement of Parallel Access Volumes (PAV), multiple requesting entered the mainstream.

References

Winchester technology

I think that Winchester technology is not adequately described. The huge advantage of Winchester technology is that the heads and the platters are all in a sealed container. The article (currently) says Winchester technology allowed the head to land and take off from the disk media as the disk spun up and down but that is far from saying that they were all contained in a safe package, protected from the outside. Sam Tomato (talk) 00:48, 14 September 2021 (UTC)

Before Winchester, disks packs were demountable. On power up, or when mounting a pack, various steps are done to make sure that the pack is clean enough (dust removed), and the the heads enter the pack and I/O operations begin. Early on, similar to tape, the idea of a permanently mounted pack doesn't seem to have been important. (Other than for NASA, I don't know of tape drives with permanently mounted tape.) It might be that there is one with removable head-disk assembly that is sealed, but otherwise allows a connection to the actuator. In any case, permanently mounted disks ended up common, and so a non-removable pack made sense. Once you do that, having a sealed HDA, is possible, and the ability to land the heads on the disk, unlike earlier drives, also makes sense. So, the ability to land on the disk surface was a major advance, and that allowed for the sealed system with permanently mounted disk. (Anyone remember the ZIP drive?) Gah4 (talk) 06:42, 14 September 2021 (UTC)

Before Winchester there were drives other than disk pack drives where the media was not removable ("demountable"}, including but not limited to the first disk drive. The first Winchester medium, the 3348 Data Module, was removeable and not sealed as disk drives are today. It was marginally better sealed than cartridges and disk packs; As it loaded into the drive a roll top door opened to allow the actuator to connect to the head stack. An advantage but not so huge. The head remaining with the disk was the huge advantage, it was enabled by the low load and lubrication that allowed the head to take off and land on the disk and thereby remain associated with the disk and not have to deal with the problems associated with interchanging. The 3350 then first used Winchester technology in a "fixed" disk drive. With a few exceptions it isn't until today's helium filled HDDs that we truly have a "sealed" HDA. Tom94022 (talk) 07:14, 14 September 2021 (UTC)

head to disk spacing?

Could we mention the head to disk spacing for some drives? Maybe even add it to a table, so we could compare? This spacing is mostly what determines the linear bit density. Gah4 (talk) 02:01, 5 November 2024 (UTC)

I would oppose adding this one of the many parameters that determine the areal density of a particular drive. I suppose including areal density where known might be useful but even that is a lot of info that is not particularly relevant to this already overly long article. Note areal density is already in the IBM's first HDD versus its last HDDs section. Tom94022 (talk) 19:47, 5 November 2024 (UTC)

How many platters on IBM 350?

The section on the IBM 350 says "It has fifty-two 24-inch (610 mm) diameter disks of which 100 recording surfaces are used, omitting the top surface of the top disk and the bottom surface of the bottom disk." But 52 disks collectively have 104 surfaces, and if you omit two of them for the top surface of the top disk and bottom surface of the bottom disk, you're left with 102, not 100, recording surfaces. Did it actually have 51 disks and 100 recording surfaces, or 52 disks and 102 recording surfaces? (I'm guessing the former but hopefully someone knows, or can find out, for sure.) DKMell (talk) 08:33, 15 November 2024 (UTC)

@DKMell: Fifty-two has been here for a long time so it's likely correct; regardless the information is readily available at Bitsavers (when it's up) so why don't you go there and answer your own question rather than delegate it to other editors? Tom94022 (talk) 07:29, 17 November 2024 (UTC)