Peripheral storage system having multiple data transfer rates

Claim 1

A peripheral data-storage system having a caching data buffer connected to a backing data store with a given minimal data-transfer rate, means for transferring data between said caching data buffer and said backing store, means for connecting said data-storage system to a plurality of peripheral channels, some of said peripheral channels being fast channels with maximal data-transfer rates of not less than said given data-transfer rate and others of said peripheral channels being slow channels having maximal data-transfer rates less than said given data-transfer rate; system control means coupled to said connecting means, said caching buffer and said backing data store, means in said control means for receiving operation-mode-indicating signals from said connecting means which indicate respective given desired modes of operation relating to usage of said caching buffer during ensuing data transfers between said channels and said data-storage system, said data buffer having a plurality of allocatable and addressable data-storage areas; fast-control means in said system control means and being responsive to said mode-indicating signals and to said ensuing data transfers with a fast one of said channels to remove data from and limit data transfers to said caching buffer in accordance with said ensuing data transfers and said operation-mode-indicating signals; buffer-data replacement-control means in said system control means for keeping an LRU list in accordance with data transfers between any of said channels and said caching buffer such that one end of the LRU list identifies data stored in said data buffer that is most-recently used while the other end of said LRU list identifies data stored in said data buffer that is least-recently used and having means for transferring data between said caching buffer and said backing store in accordance with said LRU list, said operation-mode-indicating signals and said ensuing data transfers; and slow-control means in said system control means for being responsive to said ensuing data transfers with a slow one of said channels to require all of said slow-channel-related data transfers to include said caching buffer and being further responsive to said operation-mode-indicating signals and said slow-channel-related ensuing data transfers to adjust said LRU list in accordance with said operation-mode-indicating signals and said slow-channel-related ensuing data transfers whereby even when said operation-mode-indicating signals indicate reduced desired usage of said caching buffer data occupancy in said caching buffer for fast-channel ensuing data transfers and for slow-channel ensuing data transfers that replacement of data from said caching buffer is adjusted in accordance with said operation-mode-indicating signals for all of said channels.

Claim 57

A method of operating a data-storage hierarchy having a fast front store and a backing store coupled to the front store for transferring data signals therewith, said backing store having a given data-transfer rate, slow-channel means connected to said hierarchy for transferring data signals therewith at a rate less than said given rate, fast-channel means connected to said hierarchy for transferring data signals therewith at rates including said given rate; the improvement including the steps of: when firstly transferring data between said backing store and said slow-channel means, storing all of such data in said front store as a step in said first data transfers; and when secondly transferring data between said backing store and said fast-channel means, storing only predetermined data in said front store as a step in said second data transfers including selecting said predetermined data from said secondly transferred data in accordance with predetermined criteria such that less than all of said secondly transferred data is stored in said front store as an incident to said second data transfers.

Claim 58

A method of operating a data-storage hierarchy having a fast front store and a backing store coupled to the front store for transferring data signals therewith, said backing store having a given data-transfer rate, slow-channel means connected to said hierarchy for transferring data signals therewith at a rate less than said given rate, fast-channel means connected to said hierarchy for transferring data signals therewith at rates including said given rate; the improvement including the steps of: when firstly transferring data between said backing store and said slow-channel means, storing all of such data in said front store as a step in said first data transfers; and when secondly transferring data between said backing store and said fast-channel means, storing only predetermined data in said front store as a step in said second data transfers including selecting said predetermined data from said secondly transferred data in accordance with predetermined criteria such that less than all of said secondly transferred data is stored in said front store as an incident to said second data transfers.

Claim 61

The method set forth in claims 50, 51 or 52 wherein said front store has a plurality of allocatable and addressable data storage areas; further including the steps of: ordering identifications of said allocatable data storage areas within a list in accordance with recent usages of the respective allocatable data storage areas by either said fast- or slow-channel means; maintaining said ordered list in accordance with ensuing data transfers between the front store and any of said channel means; promoting data from said backing store to said front store for said fast- and slow-channel means in accordance with first predetermined criteria related to data transfers associatable with the respective fast-and slow-channel means; replacing data stored in said front store with data from said backing store in accordance with said data promotions and demoting data from said front store to said backing store in accordance with said ordered list and independent of whether data stored in said front store to be replaced or demoted was been stored in said front store through data transfers associatable with fast- or slow-channel means.

Claim 65

The method set forth in claims 50 or 56, further including the steps of: receiving a first mode-indicating signal from a one of said channel means; responding to said received one mode-indicating signal during predetermined ensuing data transfers with a fast-channel means by altering modes of operating said data storage hierarchy by adjusting the then current operational relationships between said front store, said backing store and said fast-channel means for facilitating data transfers between said backing store and said fast-channel means; and responding to said one mode-indicating signal for data transfers with a slow-channel means by altering the then current operations of said data storage hierarchy by adjusting the operational relationships between said front store, said backing store, and said slow-channel means for limiting the data storage contents of said front store in predetermined ensuing data transfers of said data storage hierarchy with said slow-channel means.

Claim 66

The method set forth in claims 50 or 56, further including the steps of: transferring data with each of said channel means in a chain of commands associatable with a set of data transfers; and upon the completion of said transferring data in said chain of commands, adjusting the data contents of said front store by replacing data stored in said front store at the completion of said chain of commands with predetermined data from said backing store and by demoting a first predetermined portion of such front stored data from said front store to said backing store and erasing a second predetermined portion of such data from said front store all in accordance with recency of usage of such data stored in the front store by any of said channel means and adjusting said data hierarchy operations within a chain of commands in accordance with predetermined criteria received from a channel means operationally associated with such chain of commands.

Claim 67

The method set forth in claims 50 or 56, further including the steps of: receiving a data-access request from any one of said channel means; examining the data contents of said front store for the received data-access request, if the data to be accessed is stored in said front store or data storage areas of said front store are currently allocated for such received data-access request, responding to said data-access request by accessing said front store for a data transfer; if the examination of said front store shows no allocation of a data-storage area or data contents for the received data-access request, then for a data-access request received from a fast-channel means bypassing the front store and accessing the backing store to the exclusion of said front store for the received data-access request while for a slow-channel means promoting data from said backing store to said front store or allocating space in said front store for enabling the data-storage hierarchy to respond to said received data-access request.

Claim 69

The method set forth in claims 50, 51, or 55, further including the steps of: receiving from a one of said channel means a bind signal for indicating predetermined data is to be bound to said front store; storing and maintaining data identified with said bind signal in said front store; and keeping copies of such bound data in said front store and back store in a congruent form so long as said bind signal is effective.

Claim 70

The method set forth in claims 50 or 56 further including the steps of: receiving from a one of said channel means an inhibit cache-load signal with an identification of a portion of said backing store which contains data or may contain data associatable with said inhibit cache-load signal; in responding to subsequently received data-access requests relating to said identified portion, inhibit promoting data from said backing store to said front store for data transfers associatable with said fast-channel means but for data transfers associatable with said slow-channel means promoting data to said front store and then promptly removing the data from said front store after transferring it to said slow-channel means.

Claim 71

The method set forth in claims 50 or 56, further including the steps of: receiving from a one of said channel means a bypass signal together with an identification of data storage areas of said backing store associatable with said bypass signal; transferring data in predetermined subsequent data transfers with a fast-channel means by accessing data areas of said backing store associatable with said bypass signal and transferring data directly between said backing store and said fast-channel means to the exclusion of said front store; and transferring data in second predetermined data transfers between a slow-channel means and said identified storage areas of said backing store by transferring data between said backing store, said front store, and said slow-channel means whereby said front store acts as a buffer between the slow-channel means and said backing store, then upon completion of said data transfers in accordance with predetermined recently usage characteristics of data stored in said front store, removing such transferred data from said front store.

Claim 72

The method set forth in claims 50 or 56, further including the steps of: receiving from a one of said channel means a sequential bit signal for indicating that data to be transferred in a given set of ensuing data transfers is sequential data; for all data within said predetermined set of data transfers, whether such ensuing data transfers are with a fast-channel means or a slow-channel means, transferring data from said backing store to said front store upon completion of a given data transfer within said set of data transfers which has a given logical relationship to said given completed data transfer.

Claim 76

The method of operating a peripheral data-storage system having a caching buffer coupled to a plurality of large-capacity-data-storage devices for storing data in track-related data units and adapted to be connected to fast and to slow peripheral channels; the slow channels having data-transfer rates less than a minimal data transfer rate of said data-storage devices and the fast-channel having data-transfer rates equal to or exceeding said minimal data-transfer rate; including the steps of: indicating predetermined data which need not be stored in said buffer, for data being transferred over said fast channel, promoting data from said devices to said buffer in a manner to discourage write hits and encourage read hits of storage accesses to the peripheral system for encouraging direct access to said devices for data transfers with said fast channel and such that said predetermined data is directly transferred between said devices and said fast channel; transferring all data to be transferred with said slow channel through said buffer, including for said predetermined data, primarily storing data as entire track-related data units in said buffer, then replacing said predetermined data stored in said buffer more quickly than replacing other data stored in said buffer; demoting all data from said buffer to said devices for all kinds of data using a common least-recently used replacement control independent of the attachments to and data transfers with any specific ones of said channels.

Claim 77

The method of operating a peripheral data-storage system having a caching buffer coupled to a plurality of large-capacity-data-storage devices for storing data in track-related data units and adapted to be connected to fast and to slow peripheral channels; the slow channels having data-transfer rates less than a minimal data transfer rate of said data-storage devices and the fast-channel having data-transfer rates equal to or exceeding said minimal data-transfer rate; including the steps of: indicating predetermined data which need not be stored in said buffer, for data being transferred over said fast channel, promoting data from said devices to said buffer in a manner to discourage write hits and encourage read hits of storage accesses to the peripheral system for encouraging direct access to said devices for data transfers with said fast channel and such that said predetermined data is directly transferred between said devices and said fast channel; transferring all data to be transferred with said slow channel through said buffer, including for said predetermined data, primarily storing data as entire track-related data units in said buffer, then replacing said predetermined data stored in said buffer more quickly than replacing other data stored in said buffer; demoting all data from said buffer to said devices for all kinds of data using a common least-recently used replacement control independent of the attachments to and data transfers with any specific ones of said channels.

Claim 89

The method set forth in any of claims 72, 73, 74, 75, 76, 77, 78, 79 wherein said buffer is an electronic random access memory and said backing store includes a plurality of addressable DASDs; further including the steps of: addressing said data-storage hierarchy in accordance with the address of a given one of said DASDs; and separately monitoring a series of requests for each of said addressable DASDs whereby the data in said front store is controlled in accordance with the respective addressed DASD and the type of channel accessing said respective addressed DASD.

Claim 90

The method of operating a data-storage hierarchy having a backing store having a given data-transfer rate and a caching buffer store with means to store data in said buffer based upon addressable data-storage areas of said backing store, both of said stores having a plurality of addressable data-storage areas; said hierarchy being attached to a host via a set of fast channels having at least said given data transfer rate capability and a set of slow channels having data transfer rate capabilities less than said given data transfer rate for transferring data with the host over either set of channels and receiving host supplied read or write data-access requests over either set of channels; for data-access requests received from a said slow channel, queuing data in said buffer store for later transfer to said backing store in accordance with said received write data-access requests; and analyzing said read data-acccess requests, moving data to said buffer store from said backing store in accordance with said received read data-access requests whereby subsequently received read-data access requests from either of said channels tend to relate to data stored in said buffer store.

Claim 91

The method of operating a data-storage hierarchy having a backing store having a given data-transfer rate and a caching buffer store with means to store data in said buffer based upon addressable data-storage areas of said backing store, both of said stores having a plurality of addressable data-storage areas; said hierarchy being attached to a host via a set of fast channels having at least said given data transfer rate capability and a set of slow channels having data transfer rate capabilities less than said given data transfer rate for transferring data with the host over either set of channels and receiving host supplied read or write data-access requests over either set of channels; for data-access requests received from a said slow channel, queuing data in said buffer store for later transfer to said backing store in accordance with said received write data-access requests; and analyzing said read data-acccess requests, moving data to said buffer store from said backing store in accordance with said received read data-access requests whereby subsequently received read-data access requests from either of said channels tend to relate to data stored in said buffer store.