EVENODD: An Efficient Scheme for Tolerating Double Disk Failures in RAID Architectures

We present a novel method, that we call EVENODD, for tolerating up to two disk failures in RAID architectures. EVENODD employs the addition of only two redundant disks and consists of simple exclusive-OR computations. This redundant storage is optimal, in the sense that two failed disks cannot be retrieved with less than two redundant disks. A major advantage of EVENODD is that it only requires parity hardware, which is typically present in standard RAID-5 controllers. Hence, EVENODD can be implemented on standard RAID-5 controllers without any hardware changes. The most commonly used scheme that employes optimal redundant storage (i.e., two extra disks) is based on Reed-Solomon (RS) error-correcting codes. This scheme requires computation over finite fields and results in a more complex implementation. For example, we show that the complexity of implementing EVENODD in a disk array with 15 disks is about 50% of the one required when using the RS scheme. The new scheme is not limited to RAID architectures: it can be used in any system requiring large symbols and relatively short codes, for instance, in multitrack magnetic recording. To this end, we also present a decoding algorithm for one column (track) in error

South Dublin County Profile (NIRSA) Working Paper Series. No. 14

The main objective of this report is to provide a comprehensive assessment of the current situation in order to assist South Dublin County Development Board in the preparation of its strategy for economic, social and cultural development over the next ten years. The city and environs of Dublin now extend over a very extensive area, exceeding the boundaries of the Dublin administrative units. It represents a complex and dynamic functional entity with roles as both the national capital and the principal international gateway for the country. Since the mid 1990s the old county Dublin has been divided into four units for purposes of public administration, within each of which a City/County Development Board was established in 1999. As each Board is required to prepare a strategy for economic, social and cultural development, the approach adopted here is to provide an analysis that takes account of the wider context while also providing detailed small area analysis for the wards/DEDs of the CDB area

Dún Laoghaire Rathdown County Profile (NIRSA) Working Paper Series. No. 16

The main objective of this report is to provide a comprehensive assessment of the current situation in order to assist Dún Laoghaire Rathdown County Development Board in the preparation of its strategy for economic, social and cultural development over the next ten years. The city and environs of Dublin now extend over a very extensive area, exceeding the boundaries of the Dublin administrative units. It represents a complex and dynamic functional entity with roles as both the national capital and the principal international gateway for the country. Since the mid 1990s the old county Dublin has been divided into four units for purposes of public administration, within each of which a City/County Development Board was established in 1999. As each Board is required to prepare a strategy for economic, social and cultural development, the approach adopted here is to provide an analysis that takes account of the wider context while also providing detailed small area analysis for the wards/DED’s of the CDB area

Fingal County Profile (NIRSA) Working Paper Series. No. 17

The main objective of this report is to provide a comprehensive assessment of the current situation in order to assist Fingal County Development Board in the preparation of its strategy for economic, social and cultural development over the next ten years. The city and environs of Dublin now extend over a very extensive area, exceeding the boundaries of the Dublin administrative units. It represents a complex and dynamic functional entity with roles as both the national capital and the principal international gateway for the country. Since the mid 1980s the old county Dublin has been divided into four units for purposes of public administration, within each of which a City/County Development Board was established in 1999. As each Board is required to prepare a strategy for economic, social and cultural development, the approach adopted here is to provide an analysis that takes account of the wider context while also providing detailed small area analysis for the wards/DEDs of the CDB area

Dublin City Profile (Dublin County Borough) (NIRSA) Working Paper Series. No. 15

The main objective of this report is to provide a comprehensive assessment of the current situation in order to assist the City Development Board in the preparation of its strategy for economic, social and cultural development over the next ten years. The city of Dublin now extends over a very extensive area, far exceeding the boundary of Dublin Corporation. It represents a complex and dynamic functional entity with roles as both the national capital and the principal international gateway for the country. Since the early 1990’s the old county Dublin has been divided into four units for purposes of public administration, within each of which a City/County Development Board was established in 1999. As each Board is required to prepare a strategy for economic, social and cultural development, the approach adopted here is to provide an analysis that takes account of the wider context while also providing detailed small area analysis for the wards/DEDs of the CDB area