Methods and system for detecting data loss in a hierarchic data storage system
First Claim
1. A method for monitoring data loss in a hierarchic data storage system having multiple storage disks that define a physical storage space;
- the method comprising the following steps;
(a) mapping the physical storage space into a first virtual storage space which presents the physical storage space as multiple RAID areas that store data according to various RAID levels, individual RAID areas extending across multiple storage disks and comprising a region of physical storage space on individual storage disks, individual RAID areas being initially classified as an optimal RAID area in which data can be stored and retrieved with redundancy;
(b) mapping the first virtual storage space into a second virtual storage space which presents the physical storage space as multiple virtual blocks;
(c) monitoring the RAID areas to detect loss of stored data;
(d) upon detecting data loss within a first region of a RAID area, marking the first region as an invalid region and classifying the RAID area as a degraded RAID area in which data can be stored and retrieved in that RAID area, but without redundancy; and
(e) upon detecting data loss within a second region of the degraded RAID area, classifying the RAID area as a dead RAID area in which data cannot be recovered from the first and second regions of that dead RAID area.
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Abstract
Data loss is selectively tracked within a hierarchic data storage system having multiple storage disks that define a physical storage space. The physical storage space is mapped into a first virtual storage space which presents the physical storage space as multiple RAID areas that store data according to various RAID levels, such as RAID Level 1 (mirror redundancy) or RAID Level 5 (parity redundancy). Individual RAID areas extend across multiple storage disks and include a region of physical storage space on individual storage disks. The first virtual storage space is mapped into a second virtual storage space which presents the physical storage space as multiple virtual blocks. The RAID areas are monitored to detect data loss. Upon detecting data loss within a region of a RAID area, this first region is marked as invalid. Upon detecting data loss within a second region of the same RAID area, the data storage system will determine the extent of data loss. If the data loss is comparatively minor, the data storage system will identify the virtual block that is mapped onto the portion of the second region and mark it defective. The address of the virtual block is stored in a virtual data loss table to indicate that data stored in that block is unreliable. If the data loss in the second region is significant, or if the virtual data loss table becomes full, the data loss will cause the entire RAID area to be classified as "dead".
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Citations
19 Claims
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1. A method for monitoring data loss in a hierarchic data storage system having multiple storage disks that define a physical storage space;
- the method comprising the following steps;
(a) mapping the physical storage space into a first virtual storage space which presents the physical storage space as multiple RAID areas that store data according to various RAID levels, individual RAID areas extending across multiple storage disks and comprising a region of physical storage space on individual storage disks, individual RAID areas being initially classified as an optimal RAID area in which data can be stored and retrieved with redundancy; (b) mapping the first virtual storage space into a second virtual storage space which presents the physical storage space as multiple virtual blocks; (c) monitoring the RAID areas to detect loss of stored data; (d) upon detecting data loss within a first region of a RAID area, marking the first region as an invalid region and classifying the RAID area as a degraded RAID area in which data can be stored and retrieved in that RAID area, but without redundancy; and (e) upon detecting data loss within a second region of the degraded RAID area, classifying the RAID area as a dead RAID area in which data cannot be recovered from the first and second regions of that dead RAID area. - View Dependent Claims (2, 3)
- the method comprising the following steps;
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4. A method for monitoring data loss in a hierarchic data storage system having multiple storage disks that define a physical storage space;
- the method comprising the following steps;
(a) mapping the physical storage space into a first virtual storage space which presents the physical storage space as multiple RAID areas that store data according to various RAID levels, individual RAID areas extending across multiple storage disks and comprising a region of physical storage space on individual storage disks, individual RAID areas being initially classified as an optimal RAID area in which data can be stored and retrieved with redundancy; (b) mapping the first virtual storage space into a second virtual storage space which presents the physical storage space as multiple virtual blocks; (c) monitoring the RAID areas to detect loss of stored data; (d) upon detecting data loss within a first region of a RAID area, marking the first region as an invalid region and classifying the RAID area as a degraded RAID area in which data can be stored and retrieved in the RAID area, but without redundancy; (e) upon detecting data loss within a portion of a second region of the degraded RAID area, identifying a virtual block that is mapped onto the portion of the second region; (f) indicating that the identified virtual block is a defective virtual block; and (g) continuing to use remaining portions of the second region and any remaining regions within the degraded RAID area to store data without classifying the RAID area as dead. - View Dependent Claims (5, 6, 7, 8, 9)
- the method comprising the following steps;
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10. A method for monitoring data loss in a hierarchic data storage system having multiple storage disks that define a physical storage space;
- the method comprising the following steps;
(a) mapping the physical storage space into a first virtual storage space which presents the physical storage space as multiple RAID areas that store data according to various RAID levels, individual RAID areas extending across multiple storage disks and comprising a region of physical storage space on individual storage disks; (b) mapping the first virtual storage space into a second virtual storage space which presents the physical storage space as multiple virtual blocks; (c) monitoring the RAID areas to detect loss of stored data; (d) upon detecting data loss within a region of a RAID area, identifying a virtual block that is mapped onto a portion of the region; (e) indicating that the identified virtual block is a defective virtual block; and (f) continuing to use remaining portions of the region and remaining regions within the RAID area to store data. - View Dependent Claims (11, 12, 13, 14)
- the method comprising the following steps;
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15. A hierarchic data storage system comprising:
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a disk array having a plurality of storage disks that define a physical storage space; a disk array controller coupled to the disk array for writing data to and reading data from the storage disks; a RAID management system operatively coupled to the disk array controller for mapping first and second virtual storage spaces onto the physical storage space of the storage disks;
the first virtual storage space presenting the physical storage space as multiple RAID areas that store data according to various RAID levels, individual RAID area extending across multiple storage disks and comprising a region of physical storage space on individual storage disks;
the second virtual storage space presenting the physical storage space as multiple virtual blocks; anda data loss detector to selectively track data loss that occurs within individual RAID areas, the data loss detector including a region sync table which contains multiple indicators that represent whether individual regions are alternately (1) valid and have not experienced any data loss or (2) invalid and have experience some data loss.
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16. A hierarchic data storage system comprising:
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a disk array having a plurality of storage disks that define a physical storage space; a disk array controller coupled to the disk array for writing data to and reading data from the storage disks; a RAID management system operatively coupled to the disk array controller for mapping first and second virtual storage spaces onto the physical storage space of the storage disks;
the first virtual storage space presenting the physical storage space as multiple RAID areas that store data according to various RAID levels, individual RAID areas extending across multiple storage disks and comprising a region of physical storage space on individual storage disks;
the second virtual storage space presenting the physical storage space as multiple virtual blocks;a data loss detector to selectively track data loss that occurs within individual RAID areas, the data loss detector being configured to detect data loss within a region of a RAID area and identify in the second virtual storage space a defective virtual block that is mapped onto a portion of the region; and the data loss detector including a virtual data loss table to store a virtual address of the defective virtual block.
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17. A hierarchic data storage system comprising:
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a disk array having a plurality of storage disks that define a physical storage space; a disk array controller coupled to the disk array for writing data to and reading data from the storage disks; a RAID management system operatively coupled to the disk array controller for mapping first and second virtual storage spaces onto the physical storage space of the storage disks;
the first virtual storage space presenting the physical storage space as multiple RAID areas that store data according to various RAID levels, individual RAID areas extending across multiple storage disks and comprising a region of physical storage space on individual storage disks;
the second virtual storage space presenting the physical storage space as multiple virtual blocks;a data loss detector to selectively track data loss that occurs within individual RAID areas, the data loss detector including an active write store that maintains a list of all pending active write operations in the data storage system, a write operation being removed from the active write store upon completion; the disk array controller attempts to write data to the defective virtual block; and the data loss detector removes the defective virtual block from the virtual data loss table unless the data was lost while the write operation was pending and listed in the active write store.
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18. A hierarchic data storage system comprising:
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a disk array having a plurality of storage disks that define a physical storage space; a disk array controller coupled to the disk array for writing data to and reading data from the storage disks; a RAID management system operatively coupled to the disk array controller for mapping first and second virtual storage spaces onto the physical storage space of the storage disks;
the first virtual storage space presenting the physical storage space as multiple RAID areas that store data according to various RAID levels, individual RAID areas extending across multiple storage disks and comprising a region of physical storage space on individual storage disks;
the second virtual storage space presenting the physical storage space as multiple virtual blocks;a data loss detector to selectively track data loss that occurs within individual RAID areas, the data loss detector being configured to detect data loss within a region of a RAID area; the data loss detector including a region sync table which contains multiple sync bits for corresponding regions, individual sync bits having a first binary value to indicate that a corresponding region is a valid region and has not experienced any data loss and a second binary value to indicate that a corresponding region is an invalid region and has experienced some data loss; whereupon detection of data loss within a first region of a RAID area, a sync bit associated with the first region is set to the second binary value indicating that the first region is an invalid region and the disk array controller avoids writing data to that invalid region; the data loss detector being further configured to identify in the second virtual storage space a defective virtual block that is mapped onto a portion of a region; the data loss detector including a virtual data loss table to store a virtual address of the defective virtual block; and whereupon detection of data loss within a second region of a RAID area that already contains an invalid region, the address of the defective virtual block is added to the virtual data loss table and the disk array controller continues to access data in remaining portions of the second region and remaining regions within the same RAID area. - View Dependent Claims (19)
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Specification