The patent's inventors are Menon,
This patent was filed on
From the background information supplied by the inventors, news correspondents obtained the following quote: "The present invention relates to storage systems. More particularly, the present invention relates to a system, a method and a storage format that provides protection against uncorrectable media errors.
"FIG. 1 shows an exemplary high-
"The two primary sources of data loss from HDDs, such as the exemplary HDD shown in FIG. 1, are disk drive failure and uncorrectable media error. Data loss has been conventionally prevented by configuring storage systems having an array of multiple HDDs in a RAID configuration in which data is striped across multiple HDDs. Redundancy is built into the striping so that should any HDD fail, the data belonging to the failed HDD can be reconstructed from the remaining drives of the storage system.
"HDD storage capabilities have been increasing at a rate of between 60 and 100 percent per year. The probability of uncorrectable read errors, however, has been relatively constant at about 1 uncorrectable read error in 10.sup.14 bits. Accordingly, as HDD storage capabilities have increased, the probability of data loss due to an uncorrectable media error has become a significant factor.
"Multiple HDD storage systems configured as RAID level 5 systems are commonly deployed in the industry and can tolerate loss of a single disk HDD. While a failed HDD is being rebuilt, however, a second HDD failure or an uncorrectable media error on any of the remaining HDDs will result in data loss. Data loss caused by a second HDD failure is referred to as an 'array loss,' while data loss caused by an uncorrectable media error is referred to as a 'strip kill.' It is estimated that there will be 1.48 array losses and 2570 strip kills in a one-year period for an installed base of one million 300 GB HDDs that are configured in 8-drive RAID 5 array systems with each HDD having an MTBF of 500,000 hours. It should be noted that over 90% of media errors affect single sectors. About 5% of media errors affect two to four sectors. Very few media errors affect multiple (seven or more) sectors.
"Techniques have been proposed for reducing the probability of data loss. In particular, RAID-type protection techniques have been developed for protecting against drive failure by increasing the redundancy of the array using levels (such as RAID 51, RAID 6, RAID (3+3) and so on). When a RAID level is chosen for a storage system, factors that are considered include storage efficiency, reliability and performance. Optimizing any one of these three factors causes at least one of the other factors to become less than optimal.
"Table 1 is a comparison of the different conventional RAID techniques.
"TABLE-US-00001 TABLE 1 RAID 5 RAID 51 RAID (3 + 3) RAID 6 RAID N + 3 Drives/ 8 16 6 16 16 array Storage 87.5% 43.75% 50% 87.5% 81.25% Effi- ciency Annual 2570 6.17 .times. 10.sup.-7 8.55 .times. 10.sup.-7 1.61 7.53 .times. 10.sup.-4 Strip Kill events Annual 1.48 5.01 .times. 10.sup.-8 3.56 .times. 10.sup.-10 2.41 .times. 10.sup.-3 1.51 .times. 10.sup.-6 Array Loss events Perfor- 4 6 6 6 8 mance (IOs/ writes)
"The parameters on which the reliability calculations in Table 1 are based are an installed base of one million 300 GB disk drives each having an MTBF of 500,000 hours and a hard error rate of 1 error in 10.sup.14 bits.
"As can be seen from Table 1, a RAID) 6 system configuration provides an adequate protection against array loss events exhibiting only 2.41.times.10.sup.-3 array loss events per year. The number of strip kills (i.e., 1.61 strip kill events per year) is too many to meet the requirements of high-end storage systems. Adding another level of protection comes at a price, such as reduced storage efficiency (i.e., a RAID (3+3) or a RAID 51 system configuration) or reduced performance (i.e., a RAID N+3 system configuration).
"While RAID-type protection techniques have been developed for protecting against drive failure, RAID techniques do not protect well against uncorrectable media error and result in coarse granularity and sub-optimal tradeoffs. Consequently, what is needed is a technique that provides protection against uncorrectable media errors."
Supplementing the background information on this patent, VerticalNews reporters also obtained the inventors' summary information for this patent: "The present invention provides a technique that provides protection against uncorrectable media errors.
"The advantages of the present invention are provided by a method and a system for protecting data stored in a RAID-configured storage system from uncorrectable media errors. The RAID-configured storage system includes a plurality of storage units, such as HDDs, optical drives and/or random access memory. According to the invention, c redundancy information sectors are associated with n data information sectors, such that the c redundancy information sectors are based on the n data information sectors. The n data information sectors are written with c redundancy information sectors in a data segment on the same storage unit. The RAID-configured storage system can be configured, for example, as a RAID 6 storage system, a RAID 5 storage system, a RAID 51 storage system, a RAID 3+3 storage system or a RAID N+3 storage system. The c redundancy sectors effectively protect the n information sectors against up to c uncorrectable media errors in the n sectors. The redundancy information can be based on a Reed-Solomon code, an XOR-based code, or one-dimensional parity. The n data information sectors and the c redundancy information sectors can be arranged to be consecutive or intermingled.
"The present invention also provides a storage medium having a recording format therein having c redundancy information sectors that are associated with n data information sectors to form a segment. The c redundancy information sectors are based on the n data information sectors, and the segment is stored on a single storage unit in an array of storage units in a RAID-configured storage system."
For the URL and additional information on this patent, see: Menon,
Keywords for this news article include: Information Technology, Information and Data Loss and Recovery,
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