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Fault tolerant disk management system which tests failed disks during varied time intervals which are based upon the criticality associated with the failed disks
| Details |
Inventors: Chatterji, Sanjoy;
Assignee: Sequoia Systems, Inc. (Marlboro, MA)
Primary Examiner: Beausoliel, Jr.; Robert W.
Assistant Examiner: Palys; Joseph E.
Attorney, Agent or Firm: Wolf, Greenfield & Sacks, P.C.
A fault tolerant disk management system supports compound disks which are mirrored, so as to tolerate single point faults in any one physical disk of the compound disk. The system further minimizes the exposure of data stored on such a compound disk arising from additional single point failures in other physical disks of the compound disk. The system may be implemented as a software method for removing a physical disk from a logical compound disk without breaking up the compound disk or any mirror of which the compound disk may be a part. The removed physical disk may then be reinserted into the compound disk and mirror after repair. Further, the system provides fault responses which may be varied in accordance with an indication of criticality of each disk to the system. |
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DETAILED DESCRIPTION The present invention will be better understood by reading the following description in conjunction with the drawing.
A mirrored compound disk according to the present invention is shown in FIG.
4.
Mirrored compound disk 401 is addressed by a user as a single, logical device.
That is, when a user gives instructions to read data from or write data to such a compound disk, the user does not specify on which physical disk the operation will be performed.
Logically, the mirrored compound disk 401 is treated by a user as though it were a single, large, physical disk.
The mirrored compound disk actually comprises two compound disks 403 and 405 of equal storage capacity, which are bound to form a mirror pair 406 (FIG.
7, Step 702).
Further, each compound disk 403 and comprises a number of physical disks.
Compound disk 403 comprises physical disks 407, 409 and 411.
Compound disk 405 comprises physical disks 413, 415a and 417.
Note that physical disk 415a has been lined out, denoting a failure of physical disk 415a.
This will be discussed below.
In accordance with one aspect of the present invention, mirror pair 406 is formed as follows: the storage space of each physical disk comprising compound disk 403 has a one-to-one correspondence with the storage space within compound disk 405, even though the physical disks 407, 409, 411, 413, 415a and 417 do not necessarily have a one-to-one correspondence in their storage capacities.
Indeed, all that is required is that the storage capacities of compound disks 403 and 405 correspond; each physical disk contributing to the storage capacity of a compound disk may contribute any portion of that physical disk's storage capacity--the entire physical disk need not be used for that compound disk.
When a user requests a write operation to mirrored compound disk 401, the mirroring software then generates two write operations, one to each of compound disks 403 and 405.
Software which manages compound devices then calculates to which physical disk of each compound disk 403 and 405 the writes are directed
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