RAID LUNs 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 arrays 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 array. This is why, it is important that LUN performance is continuously monitored. This can be achieved using the RAID LUNs test. This test auto-discovers the LUNs in the storage system and reports the current state of each LUN, captures LUN errors, and measures the level of I/O activity on every LUN, so that administrators are notified of LUN-related problems well before they impact storage system performance.
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 LUN on the storage system.
Parameter | Description |
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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. |
Measurement | Description | Measurement Unit | Interpretation | ||||||||||||||||||||||||||||||||||||||||
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Health state |
Indicates how healthy this LUN currently is. |
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The values that this measure can report and their corresponding numeric values are discussed in the table below:
Note: By default, this measure reports the Measure Values discussed above to indicate the state of a LUN In the graph of this measure however, states are represented using the numeric equivalents only. |
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Operational status |
Indicates the current operational state of this LUN. |
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The values that this measure can report and their corresponding numeric values are discussed in the table below:
Note: By default, this measure reports the Measure Values discussed above to indicate the operational state of a LUN. In the graph of this measure however, operational states are represented using the numeric equivalents only. |
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Detailed operational state |
Describes the current operational state of this LUN. |
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This measure will be reported only if the API provides a detailed operational state. Typically, the detailed state will describe why the LUN is in a particular operational state. For instance, if the Operational status measure reports the value Stopping for a LUN, then this measure will explain why that LUN is being stopped. The values that this measure can report and their corresponding numeric values are discussed in the table below:
Note: By default, this measure reports the Measure Values discussed above to indicate the detailed operational state of a LUN. In the graph of this measure however, detailed operational states are represented using the numeric equivalents only. |
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Data transmitted |
Indicates the rate at which data was transmitted by this LUN. |
MB/Sec |
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IOPS |
Indicates the rate at which I/O operations were performed on this LUN. |
IOPS |
Compare the value of this measure across LUNs to know which LUN 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 LUNs. You may then want to take a look at the Reads and Writes measures to understand what to fine-tune – the load-balancing algorithm for read requests or that of the write requests. |
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Reads |
Indicates the rate at which read operations were performed on this LUN. |
Reads/Sec |
Compare the value of this measure across LUNs to know which LUN handled the maximum number of read requests and which handled the least. |
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Writes |
Indicates the rate at which write operations were performed on this LUN. |
Writes/Sec |
Compare the value of this measure across LUNs to know which LUN handled the maximum number of write requests and which handled the least. |
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Data reads |
Indicates the rate at which data is read from this LUN. |
MB/Sec |
Compare the value of these measures across LUNs to identify the slowest LUN in terms of servicing read and write requests (respectively). |
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Data writes |
Indicates the rate at which data is written to this LUN. |
MB/Sec |
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LUN busy |
Indicates the percentage of time this LUN was busy processing requests. |
Percent |
Compare the value of this measure across LUNs to know which LUN was the busiest and which LUN was not. If the gap between the two is very high, then it indicates serious irregularities in load-balancing across LUNs. |
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Average read size |
Indicates the amount of data read from this LUN per I/O operation |
MB/Op |
Compare the value of these measures across LUNs to identify the slowest LUN in terms of servicing read and write requests (respectively). |
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Average write size |
Indicates the amount of data written to this LUN per I/O operation. |
MB/Op |
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Read hit |
Indicates the percentage of read requests that were serviced by the cache of this LUN. |
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 LUN accesses, which are expensive operations, are high. |
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Write hit |
Indicates the percentage of write requests that were serviced by the cache of this LUN. |
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 LUN accesses, which are expensive operations, are high. |
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Average response time |
Indicates the time taken by this LUN to respond to I/O requests. |
Microsecs |
Ideally, this value should be low. If not, it implies that the LUN is slow. |
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Queue depth |
Indicates the number of requests that are in queue for this LUN. |
Number |
A consistent increase in this value indicates a potential processing bottleneck with the LUN. |