Host central processor with associated controller to capture...

Details Host central processor with associated controller to capture... Host central processor with associated controller to capture...

1998-09-02

2001-05-22

Lee, Thomas C. (Department: 2782)

Electrical computers and digital processing systems: multicomput

Multicomputer data transferring via shared memory

Plural shared memories

C709S210000, C710S005000, C710S036000

Reexamination Certificate

active

06237028

ABSTRACT:

This invention relates to data processing systems having two or more controllers plus a plurality of memory units and particularly to means of facilitating communication between controllers.
BACKGROUND, FEATURES
Workers in data processing are aware that systems having two or more processors and a number of memory units are commonly used (e.g. see U.S. Pat. Nos. 4,920,484, 3,676,860).
Workers are also familiar with the practice of associating one or several host central processors (CPUs) with an array of memory units via intermediate controllers (e.g. see U.S. Pat. No. 4,982,324, 4,413,317, 3,889,237, 4,183,084, 3,623,014). And, today, it is not uncommon to operatively associate an array of peripheral storage units with a host computer via an appropriate controller device,
FIG. 1
schematically suggests this for a host H and a number of like memory units D, connectible to H via a controller unit C, including suitable interfaces
1
F,
1
F′ (e.g. see ports
1
-
4
, each connected to a respective, like-numbered drive-port).
Similarly, it may often be desirable to so associate two (or more) host computers with a number of such memory units (storage devices)—e.g. as schematically indicated in
FIG. 2
, with one host H
1
coupled to an associated controller C
1
, a second host H
2
, also coupled to a respective associated controller C
2
, and memory units D. If units D are dual-ported, as here indicated, they may be connectible to either host/controller array (as indicated by the port numbers).
“SHARED MEMORY LINKAGE” (
FIG. 3
)
Now, it may become desirable to mediate the competition between two host-computers to “capture” a selected memory unit (e.g. drive), using certain mediation means. Such a mediation means is the “Shared Memory Interface” (Smi) indicated in
FIG. 3
, shown in operative relation with eight dual-ported disk drives D
0
-D
7
and a pair of host/controller arrays: host A
15
with Controller A and host A
17
with Controller B, plus suitable controller inter-faces, IPI-2, IPI-3. Workers should realize that mediation means Smi provides a communication link that allows one controller to request, or transmit, information to, or from, the other controller—here via what may be called “direct memory access” (DMA) something that requires special interfaces [e.g. additional special hardware, as “shared memory”, SM, and associated interfaces I-A, I-B, (memory typically a dedicated random access memory RAM) and special software]. Shared memory, SM, also functions as a common storage unit that can be used to maintain “data path control”; i.e. allow/disallow a host to write/read information to/from a selected disk drive.
PATH CONTROL
Workers will understand that such “Shared Memory Linkage” (as in
FIG. 3
) affords a degree of “path control”; i.e. it provides a “Master” (e.g. an A-series host computer, from Unisys Corp.) with the ability to disenable/enable, or to assign, any port of a given disk drive to an IPI-2 port of a controller.
By way of illustration, assume that in
FIG. 3
, disk drive “path control information” is sent to a shared memory module, SM, which stores (disk drive) path control information in its random access memory (RAM) and controls access. If the module isn't “busy” (e.g. if the other controller isn't updating or otherwise accessing memory SM), it will load the information received into its designated path control memory location; and will then interrupt the other controller, indicating that “path control” for this disk drive has changed (similarly, not U.S. Pat. No. 3,735,360 that describes a similar “shared memory” configuration shared by CPUs in a multiprocessor array).
Here (FIG.
3
), the host computers A
16
, A
17
may preferably comprise Unisys A
16
, A
17
computers (each dual-ported as shown), while their respective Controllers A, B may comprise compatible units such as, preferably, Unisys M-9730, with suitable interfaces. Preferably a Unisys IPI-3 type interface (“intelligent peripheral interface”) is used to intercouple each host to its controller. The eight disk drives are coupled to both controllers via a suitable interfaced for each controller, preferably a Unisys IPI-2 type unit with four ports, each port connected to two drives, as illustrated.
“NATURAL LINKING”(no special mediation hardware):
FIG. 4
is a modification of
FIG. 3
, indicating as a feature of novelty hereof, what I call “Natural Linking” (of Controller); eliminating all special linking hardware such as the Shared Memory Interface” SMi or any such dedicated RAM or any special interfaces.
A salient feature of this “Natural Linking” is that it operates “Controller-to-Controller”, using only a disk drive as its link, i.e. linking via means which are already part of the system (e.g. here only via a disk drive normally coupled to a M-9730 Controller, plus the “standard” IPI-2 interface normally used by this Controller). That is, here, the inter-controller linkage is “natural”, using an already-present disk drive unit via an IPI-2 interface which is normally used for disk control or read/write commands, This way, one controller can now, use its normal (natural) interface to communicate with the other controller, —both controllers being coupled to the two ports of each disk drive. This novel natural linkage allows a disk control unit (controller) to request or transmit information to, or from its companion controller via a selected disk drive in the already-present array of drives. Several useful, surprising advantages will be evident to workers (e.g. no special interfaces needed, only normal “IPI-2” interface as in FIG.
4
).
And, unlike the aforedescribed “Shared Memory Linkage”, so using a disk drive to transmit path control information, and to interrupt the other controller for updates, eliminates the need for dedicated RAM or other shared memory to maintain “data path control” and for other associated hardware and software. Workers will recognize that this direct, natural intercontroller linkage gives each controller a means of maintaining a resident copy of path-control information, while still maintaining a modicum of data security (at the subsystem). Further, only a minor part of disk-storage space is needed (e.g. I have found that a mere three sectors of track space on the maintenance cylinder an store all requisite data-path control information).


REFERENCES:
patent: 4747043 (1988-05-01), Rodman
patent: 4747047 (1988-05-01), Coogan et al.
patent: 4967390 (1990-10-01), Rendina et al.
patent: 5060140 (1991-10-01), Brown et al.

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