Raid-Based Disk Controllers; Windows Nt-Based Raid; Sybase Sql Server Mirroring/Duplexing - Compaq 117755-003 - ProSignia - 740 Configuration Manual

Page 6 Configuration and Tuning of Sybase System 11 for Microsoft Windows NT on Compaq Servers

1. RAID-based Disk Controllers

Y
Hardware RAID is configurable on a logical volume basis
volume is protected by the appropriate fault tolerance. The capacity reduction depends on
the size of the logical volume and the type of fault tolerance configured.
Y
Hardware RAID offers the best reliability and automatic recovery. When a drive fails, the
system continues operating. Once the failed drive is replaced, the controller automatically
rebuilds the new drive and restores the system to its full fault tolerant capabilities.
Y
Since the data protection occurs at the hardware (controller) level, there is no overhead on
the system processor. This type of RAID is totally transparent to the operating system and
the applications. With a CPU-intensive application/environment, such as Sybase SQL
Server, hardware-based fault tolerance can provide the best performance. Please refer to
Configuring Compaq RAID Technology for Database Servers white paper, published by
Compaq (Document Number 267A/0294) for a more complete discussion.

2. Windows NT-based RAID

Y
To take advantage of Windows NT-based fault tolerance, you need to have Windows NT
Server installed. The current versions of Windows NT Workstation do not provide software
based RAID.
Y
You have an option of controller duplexing, if your mirrored partition resides on a different
disk controller. Controller duplexing adds redundancy at the controller level, but you must
make sure that your mirrored partitions are on physically different drive controllers.
Y
Windows NT fault tolerance is based on logical drives (partitions). The capacity reduction
depends on the size of the logical drive and the type of fault tolerance installed.
Y
Windows NT fault tolerance offers reliability in a sense that you will not lose your data when
your disk crashes. Your system will continue running after a drive failure. However, the
recovery procedure is not automatic, and you will need to bring your system down.
Y
The data protection occurs at the operating system level, which induces an additional
overhead on the system processor. Consequently, in a CPU-intensive environment, Windows
NT fault tolerance will impact performance. Similar to hardware-based fault tolerance,
mirroring is preferred to striping with parity.

3. Sybase SQL Server Mirroring/Duplexing

Y
Sybase SQL Server mirroring is based on Sybase SQL Server devices. This offers you the
finest granularity and lowest capacity reduction due to duplicated data. Refer to Sybase SQL
Server, System Administration Guide for guidelines on choosing which devices to mirror.
Y
You have an option of controller duplexing, if you place the mirrored device on a different
disk controller.
Y
Sybase SQL Server supports both serial and noserial write mode of mirroring. When
utilizing the default, serial write mode, writes to the first device must finish before writes to
the second device begin. Changing from serial to noserial write mode allows the writes to
both devices to be queued immediately, one to each mirrored device. The noserial write
mode will incur less overhead than serial writes that results in a slight performance
improvement.
4
Logical volumes for the Compaq SMART SCSI Array controller are defined using Compaq System
Configuration Utility. Logical volumes for the Compaq SMART-2 SCSI Array controller are defined
using Compaq Array Configuration Utility
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4
. Therefore, the whole logical
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