The planning docs here - http://www.splunk.com/base/Documentation/latest/Installation/CapacityplanningforalargerSplunkdeployment - recommend the following storage hardware :
4x300GB SAS hard disks at 10,000 rpm each in RAID 10 * capable of 800 IO operations / second (IOPS)
Can anyone clarify this a bit further please? We need more I/O information: The 800IOPS sustained - is that read or write? Random or sequential? Large or small block?