VSP Lun Details Test

A logical unit number (LUN) is a unique identifier used to designate individual or collections of hard disk devices for address by a protocol associated with a SCSI, iSCSI, Fibre Channel (FC) or similar interface. LUNs are central to the management of storage space shared over a storage area network (SAN). LUN errors, poor LUN cache usage, and abnormal I/O activity on the LUNs, if not promptly detected and resolved, can hence significantly degrade the performance of the storage device. This is why, it is important to continuously monitor the LUN performance. This can be achieved using the VSP Lun Details test.

This test monitors the I/O traffic and data transfers conducted by each LUN on the storage device, and helps administrators identify irregularities in load balancing across LUNs.

Target of the test : A Hitachi VSP storage device

Agent deploying the test : A remote agent

Outputs of the test : One set of results for every LUN on the Hitachi VSP device monitored

The figure below depicts the test configuration page of this test. Click on the parameters in the figure below to know what they are and how to configure them.

Measures made by the test:
Measurement Description Measurement Unit Interpretation

I/O operations rate:

Indicates the number of read-write operations performed on this LUN per second.

IOPS

A high value for this measure is indicative of high I/O activity on the LUN. Comparing the value of this measure across LUNs can accurately reveal which LUNs are extremely busy, and also enable administrators to easily detect irregularities in load distribution across the LUNs.

Transaction rate:

Indicates the rate at which data transfers occur on this LUN.

KB/Sec

 

Sequential read hits:

Indicates the percentage of read requests served by this LUN in sequential access mode.

Percent

 

Random read hits:

Indicates the percentage of read requests served by this LUN in random access mode.

Percent

 

Sequential write hits:

Indicates the percentage of data written to this LUN in sequential access mode.

Percent

 

Random write hits:

Indicates the percentage of data written to this LUN in random access mode.

Percent

 

Cache-to-disk transfers:

Indicates the number of data transfer operations performed from the cache to this LUN.

Number

A high value for this measure is a sign of good health. A low value or a consistently decreasing value could be a cause for concern, as it indicates that the cache is not writing enough data to the disk; this in turn could overload the cache and hamper its ability to make space for data that is waiting to be written.

Response time:

Indicates the current responsiveness of this LUN to I/O requests.

Microseconds

Ideally, the value of this measure should be low.