Another significant direction in storage technology is the availability of storage subsystems that present a single device appearance to the operating system, but internally use many disks and gigabytes of cache memory to hide device boundaries and mask failures. With a single logical device capable of storing hundreds of gigabytes and transfer rates of hundreds of megabytes per second, the pure
In this section, I discuss a few aspects of the required hardware configuration for a parallel processing platform.
HP, Sun, and Digital 64-bit UNIX provide for an instantaneous redundant host. In the event of a system-wide failure, a "switchover" of the production UNIX servers disks and software can be transferred to a development host automatically. The HP Switch Over daemon sends a regularly scheduled signal or "heartbeat" and receives state-of-health diagnostic information in response to that signal, or absence of a signal to the standby host.
When the standby host determines that the messages have
The DEC Alpha file servers 2100, 8200, and 8400,
Remote storage devices should not be used in parallel processing because they must interface with at least the two (2) file servers. Any read/write activity is effectively
Remote file systems must also interface with the network router, cable, connectors,
The number of physical disks mounted and available to the file system are critical to the performance of Oracle and
The physical and not logical volume devices are used to balance the I/O of the background Oracle processes across the disks.
Physical disks may be "partitioned" or configured by a logical device manager in
Before you install Oracle, check with your operating system administrator for
The system tablespace, rollback segments, control files, and redo logs are always active for every Oracle instance. If Archive mode is enabled, then transaction logging will "journal" all data-base activity enabling a point-in-time recovery if needed, in conjunction with your full database backup. Archive mode should write to a duplexed tape and disk media. The
These processes use specific files, which should be distributed across different disk drives for optimal database speed.
Be certain that all Oracle background and foreground processes have the same operating system process priority. Contention will arise as a high-priority process waits for a low-priority process, which may never swap back in.
The optimum number of disks for the Oracle installation should at a minimum enable the separation of the table data on disk one and the index data on disk two, in any
With additional disk availability, the Oracle system offers tablespace on disk three, rollback segments on disk four, temporary tablespace on disk five, and the redo logs on disk six.
Time zones and business application groups should influence the tablespace design so that a database maintenance window for one application does not interfere with the operation of 7/24 maximum availability systems.
The Oracle disk storage devices in Table 56.2 can be standard devices, mirrored devices, Write Once Read Many optical disc (WORM), Write Many Read Many optical disc (WMRM), Redundant Arrays of Independent Disks (RAID) and other media types. These disks should have relatively high read/write rate (8_9
The media read and write rates for optical storage are significantly slower and therefore should not be used as high-performance file system devices for normal database query activity. These optical devices are very well suited for
Table 56.2. Storage device pricing and performance.
|Disk/Tape Storage Media Type||Storage Maximum, Gigabytes||Average Access Time, Milliseconds||Average Write Time, Milliseconds||Media Device Driver Cost|
|Standard "Barracuda" Ultra/Wide 40MB@Second||4GB||8 MS||8 MS||$995.00|
|Optical WORM 12 inch||25GB||135 MS||68 MS||$4,995.00|
|Cybernetics 2500 Optical WMRM 5.25 inch||1.3GB||19.8 MS||500 KBS||$3,495.00|
|Cybernetics CY-8505 8mm tape||25GB||67.5 S||12-90M@min.||$4,250.00|