Compaq ProLiant 1000 Configuration and Tuning of Sybase System 11 for NetWare - Page 13

Configuration and Tuning of Sybase System 11 for NetWare on Compaq Servers Page 9 Fault Tolerance Considerations Your transaction log needs to always be protected against a disk failure. Most mission critical sites protect both the transaction log and the database devices and they usually choose hardwarebased fault tolerance. Non-mission critical sites are often satisfied with the protection of the transaction log only and performing frequent backups/dumps. You have three choices of protecting your data: s Use a RAID-based disk controller such as the Compaq SMART and SMART-2 SCSI Array Controllers s Use NetWare disk controller duplexing s Use Sybase SQL Server-based mirroring/duplexing. Below are some key points to be aware of when choosing the appropriate fault tolerant method. The performance differences between fault tolerance implementations can vary from insignificant to very significant, depending on your configuration and environment. Therefore, we omitted supplying performance differences for the purpose of not misleading our readers. We recommend that you evaluate the various fault tolerance methods using your own applications. 1. RAID-based Disk Controllers Y Hardware RAID is configurable on a logical volume basis. Therefore, the whole logical 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 the Compaq TechNote Configuring Compaq RAID Technology for Database Servers for a more complete discussion. 2. NetWare Disk Controller Duplexing Y Operating system level mirroring through NetWare offers good reliability and provides fault tolerance when a disk controller should fail but it requires manual intervention for recovery. When a drive or disk controller fails, the system continues operating. To replace the failed drive or controller the server needs to be stopped and restarted. NetWare will then automatically re-synchronize the mirrored drive volume. Y Mirroring through NetWare induces an additional processing overhead on the system, resulting in a lower performance. 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. © 1996 Compaq Computer Corporation, All Rights Reserved Doc No 140A/0896