RAID Disks Test

This test monitors the current state, overall health, and the load-balancing capability of each disk in the storage system. With the help of this test, administrators can not only identify failed disks, but can also predict the potential failure of a disk, so that efforts can be undertaken to avert the same. In addition, the test also points administrators to disks that are handling more I/O requests than the rest, thus shedding light on irregularities in the distribution of I/O load across disks and prompting administrators to fine-tune the load-balancing algorithm. In addition, the test also proactively alerts administrators to probable slowdowns in I/O processing by specific disks, thereby enabling administrators to initiate pre-emptive actions.

Target of the test : An SMI-S compliant storage device

Agent deploying the test : A remote agent

Outputs of the test : One set of results for each disk on the storage system.

Configurable parameters for the test
Parameter	Description
Test period	How often should the test be executed
Host	The IP address of the storage device.
Port	The port number at which the storage device listens to. By default, this is NULL.
User and Password	Specify the credentials of a user who has the right to execute API commands on the storage device and pull out metrics. The exact role that is to be assigned to such a user will differ from one device to another – for instance, when monitoring 3PAR, you will have to provide the credentials of a user who has been assigned the Monitor role, here.
Confirm Password	Confirm the password by retyping it here.
SSL	Set this flag to Yes, if the storage device being monitored is SSL-enabled.
IsEmbedded	If this flag is set to True, it indicates that the SMI-S provider is embedded on the storage platform. On the other hand, if this flag is set to False, it indicates that the SMI-S provider has been implemented as a proxy.
SerialNumber	If the SMI-S provider has been implemented as a proxy, then such a provider can be configured to manage multiple storage devices. This is why, if the IsEmbedded flag is set to False, you will have to explicitly specify which storage system you want the eG agent to monitor. Since each storage system is uniquely identified by a SerialNumber, specify the same here. The format of this number and where you can find it will differ from one storage system to another. You are hence advised to contact the storage administrator to know what to enter against SerialNumber. For example, the serial number for an EMC CLARiiON device will be of the format, FCNMM094900059.
NameSpace	Specify the namespace that uniquely identifies the profiles specific to the provider in use.

Measurements made by the test

Measurement

Description

Measurement Unit

Interpretation

Health state

Indicates how healthy this disk currently is.

The values that this measure can report and their corresponding numeric values are discussed in the table below:

Numeric Value	Measure Value
0	OK
1	Unknown
2	Degraded/Warning
3	Minor failure
4	Major failure
5	Critical failure
6	Non-recoverable error

Note:

By default, this measure reports the Measure Values discussed above to indicate the state of a disk. In the graph of this measure however, states are represented using the numeric equivalents only.

Operational status

Indicates the current operational state of this disk.

The values that this measure can report and their corresponding numeric values are discussed in the table below:

Numeric Value	Measure Value
0	OK
1	In Service
2	Power Mode
3	Completed
4	Starting
5	Dormant
6	Other
7	Unknown
8	Stopping
9	Stressed
10	Stopped
11	Supporting Entity in Error
12	Degraded or Predicted Failure
13	Predictive Failure
14	Lost Communication
15	No Contact
16	Aborted
17	Error
18	Non-Recoverable Error

Note:

By default, this measure reports the Measure Values discussed above to indicate the operational state of a disk. In the graph of this measure however, operational states are represented using the numeric equivalents only.

Detailed operational state

Describes the current operational state of this disk.

This measure will be reported only if the API provides a detailed operational state.

Typically, the detailed state will describe why the disk is in a particular operational state. For instance, if the Operational status measure reports the value Stopping for a disk, then this measure will explain why that disk is being stopped.

The values that this measure can report and their corresponding numeric values are discussed in the table below:

Numeric Value	Measure Value
0	Online
1	Success
2	Power Saving Mode
3	Write Protected
4	Write Disabled
5	Not Ready
6	Removed
7	Rebooting
8	Offline
9	Failure

Note:

By default, this measure reports the Measure Values discussed above to indicate the detailed operational state of a disk. In the graph of this measure however, detailed operational states are represented using the numeric equivalents only.

Data transmitted

Indicates the rate at which data was transmitted by this disk.

MB/Sec

IOPS

Indicates the rate at which I/O operations were performed on this disk.

IOPS

Compare the value of this measure across disks to know which disk handled the maximum number of I/O requests and which handled the least. If the gap between the two is very high, then it indicates serious irregularities in load-balancing across disks.

You may then want to take a look at the Reads and Writes measure to understand what to fine-tune – the load-balancing algorithm for read requests or that of the write requests.

Reads

Indicates the rate at which read operations were performed on this disk.

Reads/Sec

Compare the value of this measure across disks to know which disk handled the maximum number of read requests and which handled the least. If the gap between the two is very high, then it indicates serious irregularities in load-balancing across disks.

Writes

Indicates the rate at which write operations were performed on this disk.

Writes/Sec

Compare the value of this measure across disks to know which disk handled the maximum number of write requests and which handled the least. If the gap between the two is very high, then it indicates serious irregularities in load-balancing across disks.

Data reads

Indicates the rate at which data is read from this disk.

MB/Sec

Compare the value of these measures across disks to identify the slowest disk in terms of servicing read and write requests (respectively).

Data writes

Indicates the rate at which data is written to this disk.

MB/Sec

Disk busy

Indicates the percentage of time this disk was busy processing requests.

Percent

Compare the value of this measure across disks to know which disk was the busiest and which disk was not. If the gap between the two is very high, then it indicates serious irregularities in load-balancing across disks.

Average read size

Indicates the amount of data read from this disk per I/O operation

MB/Op

Compare the value of these measures across disks to identify the slowest disk in terms of servicing read and write requests (respectively).

Average write size

Indicates the amount of data written to this disk per I/O operation.

MB/Op

Read hit

Indicates the percentage of read requests that were serviced by the cache of this disk.

Percent

A high value is desired for this measure. A very low value is a cause for concern, as it indicates that cache usage is very poor; this in turn implies that direct disk accesses, which are expensive operations, are high.

Write hit

Indicates the percentage of write requests that were serviced by the cache of this disk.

Percent

Average response time

Indicates the time taken by this disk to respond to I/O requests.

Microsecs

Ideally, this value should be low. If not, it implies that the disk is slow.

Queue depth

Indicates the number of requests that are in queue for this disk.

Number

A consistent increase in this value indicates a potential processing bottleneck with the disk.