Checking Disk I/O Rate - Compaq 108164-003 - ProLiant - 800 White Paper

Page 14 Configuration and Tuning of Sybase System 11 for NetWare on Compaq Servers
measured rates of up to 90 random I/Os per second per drive, some of which were being
temporarily cached by the Array Accelerator.

Checking Disk I/O Rate

Try not to overload any individual disk with random I/Os. To determine the I/O rate per drive,
first determine the number of I/O's per second to each logical volume. The Novell Monitor
utility reports on the number of concurrent disk requests that are queued but doesn't tell you on
which database device the I/O is occurring on. The Sybase SQL Monitor utility can determine
the I/O rate per database device.
It is best to use values from the SQL Monitor averaged over a period of time to calculate I/O
rates. Using the above output as an example, the calculations for determining the number of
sequential writes to the transaction log device are relatively simple.
The transaction log is located on a single logical volume consisting of 2 2.1GB drives attached to
the SMART-2 Array Controller. The log volume is using RAID1 for fault tolerance. From
Sybase SQL Monitor the log device shows zero reads and 94 writes.
Log device I/O: (0 reads + (94 writes * 2 writes per volume for RAID1)) = 188 writes per
volume / 2 drives per volume = 94 writes per drive < 160 maximum sequential writes per
2.1GB drive
Now lets calculate the I/O rate for the data devices. The data devices are located on single logical
volume consisting of 14 2.1GB drives attached to a second SMART-2 Array Controller. The
volume is using RAID5 for fault tolerance. Sybase SQL Monitor show the following I/O device
rates for the data devices:
acct1: 42 reads + 28 writes
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