Disk Latency metrics can only be configured for the cdm probe from admin Console.This feature is available from version 6.0 and higher for the cdm probe .Ensure you have the latest GA release of the cdm probe installed, then from Admin Console select the Disks node in the left hand column.
From here you can configure Disk Latency metrics in the monitors section
Disk Latency (ms)QOS_DISK_LATENCY MillisecondsThis metric is the total latency of the disk.6.0
Disk Read Latency (ms)QOS_DISK_READ_LATENCYMillisecondsThis metric is the read latency of the disk.6.0
Disk Write Latency (ms)QOS_DISK_WRITE_LATENCYMillisecondsThis metric is the write latency of the disk.6.0