RAID devices and partitioned tables

Table 5-1 and other statements in this chapter describe the Adaptive Server logical devices that map to a single physical device.

A striped RAID device may contain multiple physical disks, but it appears to Adaptive Server as a single logical device. For a striped RAID device, you can use multiple partitions on the single logical device and achieve good parallel query performance.

To determine the optimum number of partitions for your application mix, start with one partition for each device in the stripe set. Use your operating system utilities (vmstat, sar, and iostat on UNIX; Performance Monitor on Windows NT) to check utilization and latency.

To check maximum device throughput, use select count(*), using the (index table_name) clause to force a table scan if a nonclustered index exists. This command requires minimal CPU effort and creates very little contention for other resources.