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Teradata RDBMS Database Administration - NCR

NCR Teradata RDBMS Database Administration - NCR , 2004. - 616 p.
Download (direct link): teradatadatabaseadmin2004.pdf
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LUNs on Windows 2000 do not contain a boot slice; however, they contain a Master Boot Record, which contains partition layout information.

Comparison of RAID Levels

The following RAID levels are available:

Level Description
RAID 1 Uses pairs of disk drives that contain mirrored data. If one drive fails, the mirrored drives continues to operate.
RAID 5 Data is striped across the multiple disks in the rank. One block of a stripe is a parity block that the system uses to recreate data if a disk fails. Note: For LSI, a rank is sometimes 5 disks (older systems) and sometimes 4 disks (newer systems). RAID 5 does not imply 5 disks.
RAID S RAID S is the EMC implementation of RAID 4.

A comparison summary of RAID levels is provided in the following table.

Windows 2000

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Transaction Data Protection

Comparison RAID 1 RAID 5 RAID S
Operation Maintains a duplicate (mirror) disk for each disk on the system. If you configure more than one pair of disks per drive group, data is striped across both the regular disks and mirror disks. Using both regular and mirrored data, the system reads data blocks from the first available disk. Used for critical fault-tolerant transaction processing. Data is striped across the multiple disks in a rank. One block of a stripe is a parity block used to recreate data if a disk fails. Parity uses a binary exclusive-or algorithm. To determine the parity bit value, the system adds the binary values. If you lose two disks in one rank, you cannot access data on that rank because RAID 5 cannot recalculate the missing data. Similar to RAID 5, except the striping patterns are different.
Overhead Doubles the number of disks because every block has an identical copy. Requires 25% (for a 5 disk rank) or 33% (for a 4 disk rank) more space than the original unprotected storage space. Requires 33% more space than the original unprotected storage space.
Throughput Has about 1.4 times the throughput of RAID 5, given equal numbers of RAID 1 and RAID 5 disks. Must write both the data and the parity in separate operations for updates. Overlapping operations hide some of this overhead. Has about 70% of the RAID 1 throughput. Has about 70% of the EMC RAID 1 throughput and is about equal to LSI RAID 5 throughput.
Failure handling If a disk is down, the system reads/writes data from/to the mirror disk. After the disk is replaced, DAC automatically reconstructs data on the new disk from the mirrored disk. System performance is affected during data reconstruction. Data is reconstructed on- the-fly as users request data from a failed drive. If a drive is down, the system writes to the functional drives, and parity is not calculated. After you replace the failed disk, the DAC automatically reconstructs the data on the new disk via the parity scheme. System performance is affected during data reconstruction. Similar to RAID 5.
Availability Available on LSI and EMC arrays. Available on LSI arrays. Available on EMC arrays.

Teradata RDBMS Database Administration

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Transaction Data Protection

Comparison

RAID 1

RAID 5

RAID S

Management tools

If your Teradata server OS is ... THEN .
UNIX the adpxspt package contains tools to facilitate disk management, including: ace drive_status startamd
Windows 2000 use the SYMplicity package to manage the disks.

If your Teradata server OS is . THEN .
UNIX the adpxspt package contains tools to facilitate disk management, including: ace drive_status startamd
Windows 2000 use the SYMplicity package to manage the disks.

Cliques (UNIX)

A clique is a collection of nodes with shared access to the same disk arrays. Each multi-node system has at least one clique. Ideally, multiple cliques should have the same number of nodes per clique.

Nodes are interconnected via the BYNET. Nodes and disks are interconnected via shared SCSI buses and thus can communicate directly.

While the shared SCSI access is defined to the configuration, it is not actively used when the system is up and running. On a running system, each rank of disks is addressed by exactly one node.

The shared access allows the system to continue operating during a node failure. The vprocs remain operational and can access stored data.

If a node fails and then resets:

Stage Process
1 Teradata RDBMS restarts across all the nodes.
2 Teradata RDBMS recovers, the BYNET redistributes the vprocs of the node to the other nodes within the clique.
3 Processing continues while the node is being repaired.
4 Vprocs are distributed across all nodes in the system.

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Transaction Data Protection

Software Data Protection

The following sections discuss software data protection, including:

TJ protection
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