US6823336B1
Expired / Lapsed
US
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Data storage system and method for uninterrupted read-only access to a consistent dataset by one host processor concurrent with read-write access by another host processor
Assignee: EMC Corp
•
Filing: 2000-09-26
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Granted: 2004-11-23
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Expires: 2020-09-26
Abstract
Abstract A data storage system receives sets of the revisions such that each set of revisions changes the dataset from one consistent state to another. Each set of revisions is processed in a write-selected phase followed by a read-selected phase. In the write-selected phase, the revisions in each set are written to a buffer and processed to produce a directory of the set of revisions. In the read-selected phase, the revisions are read from the buffer and integrated into the dataset. When one set of revisions is in the read-selected phase, the next set of revisions is in the write-selected phase. To permit uninterrupted read-only access to a consistent state of the dataset, the data storage system responds to a request for reading specified data on a priority basis by first accessing the directory of the read-selected revisions to determine whether the specified data are in the read-selected set of revisions, and if so, the specified data are read from the read-selected set of revisions, and if not, the specified data are read from the dataset. In a preferred implementation, the sets of revisions are alternately written to either a first buffer or a second buffer, and processing of each set of revisions is switched from the write-selected phase to the read-selected phase by switching between the two buffers.
Inventors
- 👤 Sudhir Srinivasan
- 👤 Uresh Vahalia
- 👤 Uday K. Gupta
- 👤 Philippe Armangau
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 00:58
CPC Classifications
G; G06; G06F; G06F11/00; G06F11/07; G06F11/16; G06F11/20; G06F11/2053; G06F11/2056; G06F11/2064; G06F11/2071; G06F11/2074; G06F3/00; G06F3/06; G06F3/0601; G06F3/0602; G06F3/061; G06F3/0611; G06F3/0628; G06F3/0655; G06F3/0659; G06F3/0668; G06F3/0671; G06F3/0683; Y; Y10; Y10S; Y10S707/00; Y10S707/99931; Y10S707/99938; Y10S707/99951; Y10S707/99952
Claims Analysis
Total Claims: 38
Claim 1
Independent Claim
192 words
A method of operating a data storage system to provide uninterrupted read access to a consistent dataset concurrent with performing a series of revisions upon the dataset, the series of revisions including a first set of revisions followed by a second set of revisions, the dataset being in a consistent state after performing each set of revisions upon the dataset, said method comprising: a) processing the first set of revisions to build up a directory of the first set of revisions; and then b) processing the second set of revisions to build up a directory of the second set of revisions, and concurrently performing the first set of revisions upon the dataset, and concurrently performing read access to specified data in the dataset by accessing the directory of the first set of revisions to determine whether the specified data are in the first set of revisions, and upon finding that the specified data are in the first set of revisions, obtaining the specified data from the first set of revisions, and upon finding that the specified data are not in the first set of revisions, obtaining the specified data from the dataset.
Claim 2
Independent Claim
192 words
A method of operating a data storage system to provide uninterrupted read access to a consistent dataset concurrent with performing a series of revisions upon the dataset, the series of revisions including a first set of revisions followed by a second set of revisions, the dataset being in a consistent state after performing each set of revisions upon the dataset, said method comprising: a) processing the first set of revisions to build up a directory of the first set of revisions; and then b) processing the second set of revisions to build up a directory of the second set of revisions, and concurrently performing the first set of revisions upon the dataset, and concurrently performing read access to specified data in the dataset by accessing the directory of the first set of revisions to determine whether the specified data are in the first set of revisions, and upon finding that the specified data are in the first set of revisions, obtaining the specified data from the first set of revisions, and upon finding that the specified data are not in the first set of revisions, obtaining the specified data from the dataset.
Claim 3
Dependent Claim
32 words
The method as claimed in claim 1 , wherein the performing of the first set of revisions upon the dataset is suspended to give priority to the read access to the dataset.
Claim 4
Dependent Claim
42 words
The method as claimed in claim 1 , which further includes, upon completion of the performance of the first set of revision upon the dataset, performing the second set of revisions upon the dataset, and concurrently processing read access to the dataset.
Claim 5
Dependent Claim
79 words
The method as claimed in claim 3 , wherein the first set of revisions are stored in a first buffer, and the second set of revisions are stored in a second buffer, and wherein the method includes storing a third set of revisions in the first buffer, and upon completion of the performance of the first set of revisions upon the dataset, processing the third set of revisions to build up a directory of the third set of revisions.
Claim 6
Dependent Claim
76 words
The method as claimed in claim 1 , wherein the revisions are data to be written to blocks of storage, and the directory of the first set of revisions is an index of addresses of blocks of storage to be written to for the first set of revisions, and the directory of the second set of revisions is an index of addresses of blocks of storage to be written to for the second set of revisions.
Claim 7
Dependent Claim
29 words
The method as claimed in claim 1 , wherein the dataset is a file system, and at least one of the revisions is a change of a file name.
Claim 8
Dependent Claim
35 words
The method as claimed in claim 1 , which includes selecting a number of revisions to be included in each set of revisions in order to obtain a limited frequency of updating of the dataset.
Claim 9
Dependent Claim
42 words
The method as claimed in claim 7 , which includes buffering the first set of revisions and the second set of revisions, and permitting the frequency of updating of the dataset to exceed the limited frequency when required to avoid buffer overflow.
Claim 10
Independent Claim
252 words
A method of read-write access by a first host processor to a dataset in a first data storage system concurrent with uninterrupted read-only access by a second host processor to a consistent state of a copy of the dataset in a second data storage system, revisions to the dataset in the first data storage system from the read-write access also being made to the copy of the dataset in the second data storage system, the revisions including a first set of revisions followed by a second set of revisions, the dataset being in a consistent state after performing each set of revisions upon the dataset, the method comprising: a) processing the first set of revisions to build up a first directory of dataset revisions in the first set of revisions; and then b) processing the second set of revisions to build up a second directory of dataset revisions in the second set of revisions, and concurrently performing the first set of revisions upon the copy of the dataset, and concurrently performing read access on a priority basis to specified data in the dataset by accessing the first directory of dataset revisions to determine whether the specified data are in the first set of revisions, and upon finding that the specified data are in the first set of revisions, obtaining the specified data from the first set of revisions, and upon finding that the specified data are not in the first set of revisions, obtaining the data from the copy of the dataset.
Claim 11
Independent Claim
252 words
A method of read-write access by a first host processor to a dataset in a first data storage system concurrent with uninterrupted read-only access by a second host processor to a consistent state of a copy of the dataset in a second data storage system, revisions to the dataset in the first data storage system from the read-write access also being made to the copy of the dataset in the second data storage system, the revisions including a first set of revisions followed by a second set of revisions, the dataset being in a consistent state after performing each set of revisions upon the dataset, the method comprising: a) processing the first set of revisions to build up a first directory of dataset revisions in the first set of revisions; and then b) processing the second set of revisions to build up a second directory of dataset revisions in the second set of revisions, and concurrently performing the first set of revisions upon the copy of the dataset, and concurrently performing read access on a priority basis to specified data in the dataset by accessing the first directory of dataset revisions to determine whether the specified data are in the first set of revisions, and upon finding that the specified data are in the first set of revisions, obtaining the specified data from the first set of revisions, and upon finding that the specified data are not in the first set of revisions, obtaining the data from the copy of the dataset.
Claim 12
Dependent Claim
82 words
The method as claimed in claim 9 , wherein the first set of revisions are stored in a first buffer, and the second set of revisions are stored in a second buffer, and wherein the method includes storing a third set of revisions in the first buffer, and upon completion of the performance of the first set of revisions upon the copy of the dataset, processing the third set of revisions to build up a directory of the third set of revisions.
Claim 13
Dependent Claim
72 words
The method as claimed in claim 9 , wherein the revisions are data to be written to blocks of storage, and the first directory of dataset revisions is an index of addresses of blocks of storage to be written to for the first set of revisions, and the second directory of dataset revisions is an index of addresses of blocks of storage to be written to for the second set of revisions.
Claim 14
Dependent Claim
52 words
The method as claimed in claim 9 , wherein the dataset is a file system, the revisions include a change in the name of a file, and the revisions are specified by file access commands transmitted to the second data storage system from a remote mirroring facility in the first host processor.
Claim 15
Dependent Claim
40 words
The method as claimed in claim 9 , wherein the method includes selecting a number of revisions to be included in each set of revisions in order to obtain a limited frequency of updating of the copy of the dataset.
Claim 16
Dependent Claim
45 words
The method as claimed in claim 13 , wherein the method includes buffering the first set of revisions and the second set of revisions, and permitting the updating of the dataset to occur more frequently that the limited frequency when required to avoid buffer overflow.
Claim 17
Dependent Claim
68 words
The method as claimed in claim 9 , wherein the first data storage system groups the revisions of the dataset into the first set of revisions and into the second set of revisions in response to transaction commit commands from the first host processor, and the first data storage system transmits the first set of revisions and the second set of revisions to the second data storage system.
Claim 18
Dependent Claim
119 words
The method as claimed in claim 15 , wherein the first data storage system transmits the first set of revisions to the second data storage system by placing the first set of revisions in a first volume of storage in the first data storage system, mirroring the first volume of storage in the first data storage system to a second volume of storage in the second data storage system, transmitting the second set of revisions to the second data storage system by placing the second set of revisions in a third volume of storage in the first data storage system, and mirroring the third volume of storage to a fourth volume of storage in the second data storage system.
Claim 19
Dependent Claim
52 words
The method as claimed in claim 16 , which includes the first data storage system flushing the first set of revisions to the first volume of storage in response to a transaction commit command from the first host processor, and then forwarding the transaction commit command to the second data storage system.
Claim 20
Dependent Claim
50 words
The method as claimed in claim 16 , which includes the first data storage system assigning a unique sequence number to each set of revisions, and storing the sequence number for said each set of revisions when said each set of revisions is stored in one of the storage volumes.
Claim 21
Dependent Claim
45 words
The method as claimed in claim 18 , wherein each storage volume has a plurality of regions, and each sequence number is mapped to a respective one of regions for storage of the set of data revisions to which said each sequence number is assigned.
Claim 22
Dependent Claim
248 words
A data storage system comprising, in combination, data storage, and a storage controller responsive to read and write commands for accessing specified data of a dataset in the data storage, wherein each set of write commands modifies the dataset from one consistent state to another, and the storage controller is programmed to respond to each set of write commands by first operating upon revisions of said each set of write commands in a write-selected phase and then operating upon the revisions of said each set of write commands in a read-selected phase, the storage controller building up a directory of the revisions of said each set of write commands in the write-selected phase, and the storage controller accessing the directory of the revisions of said each set of write commands in the read-selected phase, the storage controller performing the revisions of said each set of write commands in the read-selected phase upon the dataset, and concurrently responding to the read commands on a priority basis by accessing the directory of the revisions of said each set of write commands in the read-selected phase to obtain specified data from the revisions of said each set of write commands in the read-selected phase when the specified data are in the revisions of said each set of write commands in the read-selected phase, and when the specified data are not in the revisions of said each set of write commands in the read-selected phase, obtaining the specified data from the dataset.
Claim 23
Dependent Claim
248 words
A data storage system comprising, in combination, data storage, and a storage controller responsive to read and write commands for accessing specified data of a dataset in the data storage, wherein each set of write commands modifies the dataset from one consistent state to another, and the storage controller is programmed to respond to each set of write commands by first operating upon revisions of said each set of write commands in a write-selected phase and then operating upon the revisions of said each set of write commands in a read-selected phase, the storage controller building up a directory of the revisions of said each set of write commands in the write-selected phase, and the storage controller accessing the directory of the revisions of said each set of write commands in the read-selected phase, the storage controller performing the revisions of said each set of write commands in the read-selected phase upon the dataset, and concurrently responding to the read commands on a priority basis by accessing the directory of the revisions of said each set of write commands in the read-selected phase to obtain specified data from the revisions of said each set of write commands in the read-selected phase when the specified data are in the revisions of said each set of write commands in the read-selected phase, and when the specified data are not in the revisions of said each set of write commands in the read-selected phase, obtaining the specified data from the dataset.
Claim 24
Dependent Claim
125 words
The data storage system as claimed in claim 20 , wherein the data storage system further includes a first buffer and a second buffer, and the storage controller is programmed to place the revisions of said each set of write commands alternately in either the first buffer or the second buffer and to select one of the buffers to access the revisions for one of the sets of write commands currently in the read-selected phase and to select the other of the buffers to access one of the sets of write commands currently in the write-selected phase, and to switch between the buffers to switch from the read-selected phase to the write-selected phase for the revisions of each of the sets of the write commands.
Claim 25
Dependent Claim
28 words
The data storage system as claimed in claim 21 , wherein the storage controller is programmed to switch between the buffers in response to a transaction commit command.
Claim 26
Dependent Claim
40 words
The data storage system as claimed in claim 20 , wherein the data storage system is a file server, the dataset is a file system, the read commands are file access commands, and the write commands are file access commands.
Claim 27
Dependent Claim
45 words
The data storage system as claimed in claim 23 , wherein the directory of the revisions of said each set of write commands is a hierarchical data structure including at least a root directory, a subdirectory, and at least one file entry in the subdirectory.
Claim 28
Dependent Claim
141 words
A data storage system comprising, in combination: data storage, and a storage controller responsive to read and write commands for accessing specified data of a dataset in the data storage, the write commands specifying sets of revisions to be made to the dataset, wherein the storage controller is programmed to respond to transaction commit commands by alternately writing the sets of revisions to a first volume of the data storage and to a second volume of the data storage, each set of revisions to the dataset including revisions from a set of transactions defined by the transaction commit commands so that each set of revisions changes the dataset from one consistent state to another, and the storage controller is programmed with a remote mirroring facility for mirroring the first and second volumes to corresponding volumes in a remote data storage system.
Claim 29
Dependent Claim
141 words
A data storage system comprising, in combination: data storage, and a storage controller responsive to read and write commands for accessing specified data of a dataset in the data storage, the write commands specifying sets of revisions to be made to the dataset, wherein the storage controller is programmed to respond to transaction commit commands by alternately writing the sets of revisions to a first volume of the data storage and to a second volume of the data storage, each set of revisions to the dataset including revisions from a set of transactions defined by the transaction commit commands so that each set of revisions changes the dataset from one consistent state to another, and the storage controller is programmed with a remote mirroring facility for mirroring the first and second volumes to corresponding volumes in a remote data storage system.
Claim 30
Dependent Claim
80 words
The data storage system as claimed in claim 25 , wherein the storage controller is programmed to respond to a transaction commit command by flushing a current set of revisions to one of the first or second volumes, the flushing operation including the remote mirroring facility transmitting the current set of revisions from said one of the first or second volumes to the remote data storage system, and then transmitting a transaction commit command to the remote data storage system.
Claim 31
Dependent Claim
49 words
The data storage system as claimed in claim 26 , wherein the storage controller is programmed to select a number of revisions to be included in each set of revisions in order to obtain a limited frequency of transmission of transaction commit commands to the remote data storage system.
Claim 32
Dependent Claim
48 words
The data storage system as claimed in claim 27 , wherein the storage controller is programmed to permit the frequency of transmission of transaction commit commands to the remote data storage system to exceed the limited frequency when required to avoid overflow of the first and second volumes.
Claim 33
Dependent Claim
51 words
The data storage system as claimed in claim 25 , wherein the storage controller is programmed to assign a unique sequence number to each set of revisions and to store the sequence number with each set of revisions when each set of revisions is stored in one of the storage volumes.
Claim 34
Dependent Claim
53 words
The data storage system as claimed in claim 29 , wherein each of said volumes has a plurality of regions, and the storage controller is programmed to map each sequence number to a respective one of the regions for storage of the set of revisions to which said each sequence number is assigned.
Claim 35
Dependent Claim
267 words
A program storage device comprising: a program for a storage controller of a data storage system, the program being executable by the storage controller for responding to read and write commands for accessing specified data of a dataset in data storage of the data storage system, wherein each set of write commands modifies the dataset from one consistent state to another, and the program is executable by the storage controller for responding to each set of write commands by first operating upon revisions of said each set of write commands in a write-selected phase and then operating upon the revisions of said each set of write commands in a read-selected phase, the storage controller building up a directory of the revisions of said each set of write commands in the write-selected phase, and the storage controller accessing the directory of the revisions of said each set of write commands in the read-selected phase, the storage controller performing the revisions of said each set of write commands in the read-selected phase upon the dataset, and concurrently responding to the read commands on a priority basis by accessing the directory of the revisions of said each set of write commands in the read-selected phase to obtain specified data from the revisions of said each set of write commands in the read-selected phase when the specified data are in the revisions of said each set of write commands in the read-selected phase, and when the specified data are not in the revisions of said each set of write commands in the read-selected phase, obtaining the specified data from the dataset.
Claim 36
Dependent Claim
267 words
A program storage device comprising: a program for a storage controller of a data storage system, the program being executable by the storage controller for responding to read and write commands for accessing specified data of a dataset in data storage of the data storage system, wherein each set of write commands modifies the dataset from one consistent state to another, and the program is executable by the storage controller for responding to each set of write commands by first operating upon revisions of said each set of write commands in a write-selected phase and then operating upon the revisions of said each set of write commands in a read-selected phase, the storage controller building up a directory of the revisions of said each set of write commands in the write-selected phase, and the storage controller accessing the directory of the revisions of said each set of write commands in the read-selected phase, the storage controller performing the revisions of said each set of write commands in the read-selected phase upon the dataset, and concurrently responding to the read commands on a priority basis by accessing the directory of the revisions of said each set of write commands in the read-selected phase to obtain specified data from the revisions of said each set of write commands in the read-selected phase when the specified data are in the revisions of said each set of write commands in the read-selected phase, and when the specified data are not in the revisions of said each set of write commands in the read-selected phase, obtaining the specified data from the dataset.
Claim 37
Dependent Claim
128 words
The program storage device as claimed in claim 31 , wherein the data storage system further includes a first buffer and a second buffer, and the program is executable by the storage controller for placing the revisions of said each set of write commands alternately in either the first buffer or the second buffer and to select one of the buffers to access the revisions for one of the sets of write commands currently in the read-selected phase and to select the other of the buffers to access one of the sets of write commands currently in the write-selected phase, and to switch between the buffers to switch from the read-selected phase to the write-selected phase for the revisions of each of the sets of the write commands.
Claim 38
Dependent Claim
31 words
The program storage device as claimed in claim 32 , wherein the program is executable by the storage controller for switching between the buffers in response to a transaction commit command.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2007-11-23 | 2008-05-24 | 2008-11-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2011-11-23 | 2012-05-24 | 2012-11-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2015-11-23 | 2016-05-24 | 2016-11-23 | $7700.00 | Window Closed / Lapsed |