US5636359A — Performance enhancement system and method for a h…

Claim 1

Independent Claim 420 words

In a data storage system including a host computer channel coupled to a Storage Controller (SC) having a controller cache memory (CCM) for storing a plurality of data blocks containing records, the data blocks ordered according to a CCM Least Recently Used (LRU) priority list, and further having a non volatile storage (NVS) for storing backup copies of modified data records, wherein the SC is coupled to one or more Cached Storage Drawers (CSDs) each having a plurality of Head Disk Assemblies (HDAs) coupled to at least one drawer cache memory (DCM) for storing a plurality of data blocks ordered according to a DCM LRU priority list, each DCM having a backup power source, and directory means connected to the CCM for enabling the addressing of the CCM and retaining the status of data blocks, a method for transferring data between the host computer channel and the plurality of HDAs responsive to a write operation initiated by the host computer channel, the method comprising the steps of: destaging a write modified data block from the CCM to the DCM; responsive to the destaging from the CCM to the DCM, creating status information in the directory means to indicate that the modified data block has been modified and the state of the modified data block is destaged but not committed; destaging the modified data block from the DCM to a HDA; responsive to the destaging from the DCM to the HDA, signaling a commit from the CSD to the SC and resetting the status information in the directory means to indicate that the modified data block is not modified; determining the position of the modified data block in the CCM LRU priority list; responsive to a determination that the order of the modified data block in the CCM LRU priority list indicates that the modified data block is to be destaged from CCM, adding the modified data block to a CCM destage list in the directory means; responsive to a determination that the modified data block is on the CCM destage list and the status information in the directory means indicates that the modified track has been destaged but not committed, adding the modified data block to a Not committed list in the directory means; writing a dummy record into NVS to indicate that the status information in the directory means indicates that the state of the modified data block is destaged but not committed; and freeing the space in NVS allocated to a backup copy of the modified data block.

Claim 2

Dependent Claim 420 words

In a data storage system including a host computer channel coupled to a Storage Controller (SC) having a controller cache memory (CCM) for storing a plurality of data blocks containing records, the data blocks ordered according to a CCM Least Recently Used (LRU) priority list, and further having a non volatile storage (NVS) for storing backup copies of modified data records, wherein the SC is coupled to one or more Cached Storage Drawers (CSDs) each having a plurality of Head Disk Assemblies (HDAs) coupled to at least one drawer cache memory (DCM) for storing a plurality of data blocks ordered according to a DCM LRU priority list, each DCM having a backup power source, and directory means connected to the CCM for enabling the addressing of the CCM and retaining the status of data blocks, a method for transferring data between the host computer channel and the plurality of HDAs responsive to a write operation initiated by the host computer channel, the method comprising the steps of: destaging a write modified data block from the CCM to the DCM; responsive to the destaging from the CCM to the DCM, creating status information in the directory means to indicate that the modified data block has been modified and the state of the modified data block is destaged but not committed; destaging the modified data block from the DCM to a HDA; responsive to the destaging from the DCM to the HDA, signaling a commit from the CSD to the SC and resetting the status information in the directory means to indicate that the modified data block is not modified; determining the position of the modified data block in the CCM LRU priority list; responsive to a determination that the order of the modified data block in the CCM LRU priority list indicates that the modified data block is to be destaged from CCM, adding the modified data block to a CCM destage list in the directory means; responsive to a determination that the modified data block is on the CCM destage list and the status information in the directory means indicates that the modified track has been destaged but not committed, adding the modified data block to a Not committed list in the directory means; writing a dummy record into NVS to indicate that the status information in the directory means indicates that the state of the modified data block is destaged but not committed; and freeing the space in NVS allocated to a backup copy of the modified data block.

Claim 3

Dependent Claim 138 words

The method of claim 1, further comprising the step of: determining if the modified data block has been destaged from DCM to an HDA; responsive to determining the modified data block has been destaged from DCM to an HDA, freeing modified data in CCM by the following steps: resetting the status information in the directory means to indicate that the modified data block is not modified and the modified data block is no longer in the state of destaged and not committed; determining if the modified data block is on the Not committed list; and responsive to determining that the modified data block has been added to the Not committed list, placing the modified data block on the CCM LRU priority list in a position indicating that the modified data block is next to be demoted from CCM.

Claim 4

Dependent Claim 73 words

The method of claim 1 wherein previously allocated NVS space is reclaimed for use by the following steps of: determining the content of an NVS data block, and if the data block is the dummy record then issuing a commit request from the SC to the one or more CSDs; responsive to issuing the commit request in response to the dummy record, destaging the modified data blocks from the DCM to a HDA.

Claim 5

Dependent Claim 30 words

The method of claim 3, wherein the content of the NVS data block is determined to contained a modified record then scheduling the modified block to be destaged from CCM.

Claim 6

Dependent Claim 91 words

The method of claim 3, wherein if a host computer channel initiated write operation requests to further modify the modified data block after the status information in the directory means indicates that the state of the modified data block is destaged but not committed, then issuing a commit request from the SC to the one or more CSDs; and responsive to issuing the commit request in response to a host computer channel request to further modify the modified data block, destaging the modified data blocks from the DCM to a HDA.

Claim 7

Dependent Claim 57 words

The method of claim 5, further comprising the additional steps of: responsive to the destaging of the modified data blocks from the DCM to the HDA, issuing a commit reply from the one or more CSDs to the SC; and responsive to the commit reply, the SC allowing the host computer channel initiated write operation to proceed.

Claim 8

Dependent Claim 123 words

The method of claim 5, further comprising the step of: responsive to a commit reply from the CSD to the SC for the modified data block, freeing modified data in CCM and in NVS by the following steps: freeing the dummy record in the NVS; resetting the status information in the directory means to indicate that the modified data block is not modified and the modified data block state is changed from the state of destaged and not committed; and responsive to determining that the modified data block has been added to the Not committed list, placing the modified data block on the CCM LRU priority list in a position indicating that the modified data block is next to be demoted from CCM.

Claim 9

Dependent Claim 470 words

A data storage system comprising: a host computer channel for receiving requests each specifying addressed data; a Storage Controller (SC) coupled to the host computer channel for controlling data transfers between the host computer channel and a data storage means; a controller cache memory (CCM) in the SC for storing a plurality of data blocks ordered according to a CCM Least Recently Used (LRU) priority list; a non volatile store (NVS) memory for storing backup copies of modified data records; at least one Cached Storage Drawer (CSD) in the data storage means coupled to the SC for storing data; a plurality of HDAs in the CSD for storing data; a Drawer Cache Memory (DCM) in the CSD coupled to the plurality of HDAs for storing a plurality of data blocks ordered according to a DCM LRU priority list, the DCM having a backup power source; directory means connected to the CCM for enabling the addressing of the CCM and retaining the status of data blocks; machine executed means coupled to the CCM for transferring data between host computer channel and the plurality of HDAs responsive to a write operation initiated by the host computer channel, the machine executed means including: means for destaging a write modified data block from the CCM to the DCM; means responsive to the destaging from the CCM to the DCM, creating status information in the directory means to indicate that the modified data block has been modified and the state of the modified data block is destaged but not committed; means for destaging the modified data block from the DCM to a HDA; means responsive to the destaging from the DCM to the HDA, signaling a commit from the CSD to the SC and resetting the status information in the directory means to indicate that the modified data block is not modified; means for determining the position of the modified data block in the CCM LRU priority list: means responsive to a determination that the order of the modified data block in the CCM LRU priority list indicates that the modified data block is to be destaged from CCM for adding the modified data block to a CCM destage list in the directory means; and means responsive to a determination that the modified data block is on the CCM destage list and the status information in the directory means indicates that the modified track has been destaged but not committed for adding the modified data block to a Not committed list in the directory means; means for writing a dummy record into NVS to indicate that the status information in the directory means indicates that the state of the modified data block is destaged but not committed; and means for freeing the space in NVS allocated to a backup copy of the modified data block.

Claim 10

Dependent Claim 470 words

A data storage system comprising: a host computer channel for receiving requests each specifying addressed data; a Storage Controller (SC) coupled to the host computer channel for controlling data transfers between the host computer channel and a data storage means; a controller cache memory (CCM) in the SC for storing a plurality of data blocks ordered according to a CCM Least Recently Used (LRU) priority list; a non volatile store (NVS) memory for storing backup copies of modified data records; at least one Cached Storage Drawer (CSD) in the data storage means coupled to the SC for storing data; a plurality of HDAs in the CSD for storing data; a Drawer Cache Memory (DCM) in the CSD coupled to the plurality of HDAs for storing a plurality of data blocks ordered according to a DCM LRU priority list, the DCM having a backup power source; directory means connected to the CCM for enabling the addressing of the CCM and retaining the status of data blocks; machine executed means coupled to the CCM for transferring data between host computer channel and the plurality of HDAs responsive to a write operation initiated by the host computer channel, the machine executed means including: means for destaging a write modified data block from the CCM to the DCM; means responsive to the destaging from the CCM to the DCM, creating status information in the directory means to indicate that the modified data block has been modified and the state of the modified data block is destaged but not committed; means for destaging the modified data block from the DCM to a HDA; means responsive to the destaging from the DCM to the HDA, signaling a commit from the CSD to the SC and resetting the status information in the directory means to indicate that the modified data block is not modified; means for determining the position of the modified data block in the CCM LRU priority list: means responsive to a determination that the order of the modified data block in the CCM LRU priority list indicates that the modified data block is to be destaged from CCM for adding the modified data block to a CCM destage list in the directory means; and means responsive to a determination that the modified data block is on the CCM destage list and the status information in the directory means indicates that the modified track has been destaged but not committed for adding the modified data block to a Not committed list in the directory means; means for writing a dummy record into NVS to indicate that the status information in the directory means indicates that the state of the modified data block is destaged but not committed; and means for freeing the space in NVS allocated to a backup copy of the modified data block.

Claim 11

Dependent Claim 147 words

The system of claim 8, wherein the machine executed means coupled to the CCM further includes: means for determining if the modified data block has been destaged from DCM to an HDA; means responsive to determining the modified data block has been destaged from DCM to an HDA, freeing modified data in CCM by the following steps: resetting the status information in the directory means to indicate that the modified data block is not modified and the modified data block is no longer in the state of destaged and not committed; determining if the modified data block is on the Not committed list; and responsive to determining that the modified data block has been added to the Not committed list, placing the modified data block on the CCM LRU priority list in a position indicating that the modified data block is next to be demoted from CCM.

Claim 12

Dependent Claim 82 words

The system of claim 8, wherein previously allocated NVS space is reclaimed for use by the machine executed means coupled to the CCM by the following steps of: determining the content of an NVS data block, and if the data block is the dummy record then issuing a commit request from the SC to the one or more CSDs; responsive to issuing the commit request in response to the dummy record, destaging the modified data blocks from the DCM to a HDA.

Claim 13

Dependent Claim 31 words

The system of claim 10, wherein if the content of the NVS data block is determined to contained a modified record then scheduling the modified block to be destaged from CCM.

Claim 14

Dependent Claim 91 words

The system of claim 10, wherein if a host computer channel initiated write operation requests to further modify the modified data block after the status information in the directory means indicates that the state of the modified data block is destaged but not committed, then issuing a commit request from the SC to the one or more CSDs; and responsive to issuing the commit request in response to a host computer channel request to further modify the modified data block, destaging the modified data blocks from the DCM to a HDA.

Claim 15

Dependent Claim 67 words

The system of claim 12, wherein the machine executed means coupled to the CCM further includes: means responsive to the destaging of the modified data blocks from the DCM to the HDA, issuing a commit reply from the one or more CSDs to the SC; and means responsive to the commit reply for causing the SC to allow the host computer channel initiated write operation to proceed.

Claim 16

Dependent Claim 130 words

The system of claim 12, wherein the machine executed means coupled to the CCM further includes: means responsive to a commit reply from the CSD to the SC for the modified data block, freeing modified data in CCM and in NVS by the following steps: freeing the dummy record in the NVS; resetting the status information in the directory means to indicate that the modified data block is not modified and the modified data block state is changed from the state of destaged and not committed; and responsive to determining that the modified data block has been added to the Not committed list, placing the modified data block on the CCM LRU priority list in a position indicating that the modified data block is next to be demoted from CCM.

Claim 17

Dependent Claim 68 words

The system of claim 12, wherein the machine executed means coupled to the CCM further includes: means responsive to the destaging of the modified data blocks from the DCM to the HDA, for issuing a commit reply from the one or more CSDs to the SC; and means responsive to the commit reply, for signaling the SC to allow the host computer channel initiated write operation to proceed.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	2000-06-02	2000-12-02	2001-06-03	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2004-06-02	2004-12-02	2005-06-03	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2008-06-02	2008-12-02	2009-06-03	$7700.00	Window Closed / Lapsed

Performance enhancement system and method for a hierarchical data cache using a RAID parity scheme

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