 Logical view and access to physical storage in modular data and storage management system |
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| CDMA method with increased capacity |
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| Ecological system and method |
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| Waste water purifying procedure |
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| Methane production by attached film |
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| Chemical detoxification of sewage sludge |
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System and method for efficient failover/failback techniques for fault-tolerant data storage system
| Details |
Inventors: McKean, Brian D.; Otterness, Noel S.; Skazinski, Joseph G.;
Assignee: International Business Machines Corporation (Armonk, NY)
Primary Examiner: Beausoliel; Robert
Assistant Examiner: Wilson; Yolanda L.
Attorney, Agent or Firm: Ananian; R. Michael, Samodovitz; Arthur J.
Structure and method for efficient failover and failback techniques in a data storage system utilizing a dual-active controller configuration for minimizing a delay in responding to I/O requests from a host system following a controller failure is described. A stripe lock data structure is defined to maintain reservation status or stripe locks of cache lines within data extents that are part of a logical unit or storage volume. When a controller fails, dirty cache line data of a failed controller is taken over by a survivor controller. The stripe lock data structure is used to process I/O requests from a host system, by the failed controller. The data storage system functions in a single-active configuration until the dirty cache line data is flushed to one or more storage volumes, by the survivor controller. The inventive structure and method provide utilize a storage volume reservation system. The stripe lock data structure is defined in memory within each of the two or more caching controllers. The stripe lock data structure is used to provide consistent information within each of the two or more caching controllers, and the stripe lock data structure is used by a failed controller to process I/O requests from a host system until dirty cache line data is flushed to one or more storage volumes by a survivor controller. Provides a method and structure which minimizes a delay required to begin processing of host I/O request following a controller failure. |
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DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION One technique for overcoming the controller failure problem described in the Background above is a cache mirroring system, apparatus and method for a dual-active controller environment as described in co-pending U.
S.
patent application Ser.
No.
09/410,168 filed Sep.
30, 1999 and entitled System, Apparatus & Method Providing Cache Data Mirroring To A Data Storage System, assigned to the assignee of the present invention and hereby incorporated by reference.
Referring to FIG.
1, a data storage system 100 utilizing a dual-active controller configuration is depicted.
In accordance with the cache data mirror method, a Controller A (primary controller) 116 receives a write data request from the host system 102, the write data request includes data to be written by the primary controller 116 to the storage subsystem.
The primary controller 116 caches the data into the primary controller 116 cache memory 120.
Next, the primary controller 116 mirrors the data to Controller B (alternate controller) 118, such that the alternate controller 118 copies the data into an alternate controller cache memory 122, thereby providing a backup copy of the primary controllers 116 data in case of a controller failure.
Referring to FIG.
2, an exemplary controller 160 is depicted.
The controller 160 includes a CPU 162, a PROM 178, RAM memory 164, and a cache memory 172.
The cache memory 172 includes a read/write (R/W) cache area 174, and a mirror area 176.
The R/W cache area 174 is used as an intermediate storage area for cache line data in order provide the host system 100 optimized access to the cache line data without having to access the storage subsystem 108, 110.
The mirror area 176 is used to store a backup copy of cache line data (backup data) mirrored from a partner controller.
The mirror area 176 is provided to allow a survivor controller to take over the tasks and cache line data of a failed controller.
However, in the event of a controller failure, the survivor controller must perform several task before resuming processing of host I/O requests
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