v7000 VDisks Test

A volume or a VDisk is a logical disk that the clustered system presents to a host connected over a Fibre Channel or Ethernet network. These VDisks enable administrators to more efficiently manage resources. However, if a vDisk experiences a processing bottleneck, it will not be able to process I/O requests quickly, thereby causing prolonged delays in data access for users. Similarly, a vdisk that is overloaded will not be able to perform at peak capacity, thus affecting the user experience with the storage system. Administrators hence have to continuously track the load on and the I/O processing speed of each of the vdisks, so that potential overload conditions and probable processing delays can be detected proactively and pre-emptively treated. The v7000 VDisks test helps administrators with this. This test monitors the level of traffic on each vdisk on an IBM v7000 storage system, and helps isolate irregularities in load balancing across the vdisks. Alongside, the test also helps identify which vdisk is experiencing processing bottlenecks (if any), so that the bottleneck is cleared before users complain of slowdowns.

Target of the test : An IBM Storwize v7000 storage system

Agent deploying the test : A remote agent

Outputs of the test : One set of results for every VDisk being monitored.

Configurable parameters for the test

Parameter	Description
Test Period	How often should the test be executed.
Host	The host for which the test is to be configured.
Port	The port number at which the specified host listens to. By default, this is NULL.
Timeout	Specify the duration (in seconds) beyond which the test will timeout in the Timeout text box. The default value is 60 seconds.

Measurements made by the test

Measurement	Description	Measurement Unit	Interpretation
Read operations	Indicates the rate at which read operations were performed by this VDisk.	Reads/Sec	A consistent rise in the value of these measures indicates a high level of I/O activity on the VDisk. Comparing the value of each of these measures across VDisks helps you in determining whether/not the I/O load is uniformly distributed across the VDisks or one/more VDisks are handling more load than the rest. This comparative analysis could shed light on irregularities in load balancing across the VDisks.
Write operations	Indicates the rate at which write operations were performed by this VDisk.	Writes/Sec
Read data	Indicates the rate at which data blocks were read from this VDisk.	MB/Sec	A consistent drop in this value could indicate a gradual dip in the rate at which read requests are processed by the VDisk. Compare the value of this measure across VDisks to identify those VDisks that are reading slowly.
Write data	Indicates the rate at which the data blocks were written to this VDisk of this node.	MB/Sec	A consistent drop in this value could indicate a gradual dip in the rate at which write requests are processed by the VDisk. Compare the value of this measure across VDisks to identify those VDisks that are writing data slowly.
Average read latency	Indicates the average time taken by this VDisk to respond to read requests.	Millisec	Comparing the value of these measures across VDisks helps you in identifying the VDisks that are the least responsive to I/O requests and when they are the slowest – when reading? or when writing?.
Average write latency	Indicates the average time taken by this VDisk to respond to write requests.	Millisec
Average transfer latency	Indicates the average time taken by this VDisk to transfer requests during the last measurement period.	Microseconds
Maximum read response time	Indicates the maximum time taken by this VDisk to respond to a read request during the last measurement period.	Millisec	Compare the value of this measure across the VDisks to identify the VDisk that is extremely slow in responding to read requests.
Maximum write response time	Indicates the maximum time taken by this VDisk to respond to a write request during the last measurement period.	Millisec	Compare the value of this measure across the VDisks to identify the VDisk that is extremely slow in responding to write requests.