Protocol: iSCSI Operations

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This statistic shows iSCSI operations/sec (iSCSI IOPS) requested by initiators to the appliance. Various useful breakdowns are available: to show the initiator, target, type and latency of the iSCSI I/O.

When to Check iSCSI Operations

iSCSI operations/sec can be used as an indication of iSCSI load, and can also be viewed on the dashboard.

Use the latency breakdown when investigating iSCSI performance issues, especially to quantify the magnitude of the issue. This measures the I/O latency component for which the appliance is responsible for, and displays it as a heat map so that the overall latency pattern can be seen, along with outliers. If the iSCSI latency is high, drill down further on latency to identify the client initiator, the type of operation and LUN for the high latency, and, check other statistics for both CPU and Disk load to investigate why the appliance is slow to respond; if latency is low, the appliance is performing quickly, and any performance issues experienced on the client initiator are more likely to be caused by other factors in the environment: such as the network infrastructure, and CPU load on the client itself.

The best way to improve performance is to eliminate unnecessary work, which may be identified through the client initiator, lun and command breakdowns.

iSCSI Operations Breakdowns

Table 42 Breakdowns of iSCSI Operations

Breakdown	Description
initiator	iSCSI client initiator
target	Local SCSI target
project	The project for this iSCSI request.
lun	The LUN for this iSCSI request.
type of operation	iSCSI operation type. This shows how the SCSI command is transported by the iSCSI protocol, which can give an idea to the nature of the I/O.
command	SCSI command sent by the iSCSI protocol. This can show the real nature of the requested I/O (read/write/sync-cache/...).
latency	A heat map showing the latency of iSCSI I/O, as measured from when the iSCSI request arrived on the appliance from the network, to when the response is sent; this latency includes the time to process the iSCSI request, and to perform any disk I/O.
offset	A heat map showing the file offset of iSCSI I/O. This can be used to identify random or sequential iSCSI IOPS. Use the Disk I/O operations statistic to check whether random iSCSI IOPS maps to random Disk IOPS after the LUN and RAID configuration has been applied.
size	A heat map showing the distribution of iSCSI I/O sizes.

These breakdowns can be combined to produce powerful statistics. For example:

"Protocol: iSCSI operations per second of command read broken down by latency" (to examine latency for SCSI reads only)

Further Analysis

See Protocol: iSCSI Bytes for the throughput of this iSCSI I/O; also see Cache: ARC Accesses to learn how well an iSCSI read workload is returning from cache, and Disk: I/O Operations for the back-end disk I/O caused.