Investigating and measuring the impact of non-cached workflow and transfer rates (xfers) to disks will help lead to an understanding of how a unique dataset will deliver a particular result.
- Use the isi statistics drive –-nodes all –-top –-long –-orderby timeavg command to display performance statistics by drive, ordered by OpsIn and OpsOut values. Note that this command is not measuring hard drive input/output operations per second (IOPS); it measures software transfer commands to storage only. Disks manage their own physical ordering of these requests, which OneFS does not see or measure in the form of physical I/O operations (IOPS). Mentally adjust the OpsIn and OpsOut fields to reflect that reality.
- It is very important to profile your workload by using at least the isi statistics commands. Use them to understand how an application drives the workload to and from disks.
- Unfortunately, there are no available disk transfer rate numbers that can determine how much is too much to cause performance degradation. OneFS simply does not deliver data from that deep in the storage stack to make this an easy operation. Monitor on the Busy%, Queued, TimeInAQ, and TimeAvg columns returned from the isi statistics drive commands to make judgments on whether your storage layer is being overwhelmed, according to your performance requirements.