EMC Storage Product Knowledge Sharing

The Storage Processor (SP) processes all I/Os, host requests, management and maintenance tasks, as well as operations related to replication or migration features.

In Navisphere Analyzer, the statistics for an SP are based on the I/O workload from its attached hosts. It reflects the overall performance of CLARiiON storage system. The following Performance Metrics will be monitored for each CLARiiON storage system.

A LUN is an abstract object whose performance depends on various factors. The primary consideration is whether a host I/O can be satisfied by the cache. A cache hit does not require disk access; a cache miss requires one or more disk accesses to complete the data request.

As the slowest devices in a storage system, disk drives are often responsible for performance-related issues. Therefore, we recommend that you pay close attention to disk drives when analyzing performance problems.

SP performance metrics

• Utilization (%)

The percentage of time during which the SP is servicing any request.

• Total Throughput (I/O/sec)

The average number of host requests that are passed through the SP per second, including both read and write requests.




• Read Throughput (I/O/sec)

The average number of host read requests that are passed through the SP per second.

• Write Throughput (I/O/sec)

The average number of host write requests that are passed through the SP per second.

• Read Bandwidth (MB/s)

The average amount of host read data in Mbytes that is passed through the SP per second.

• Write Bandwidth (MB/s)

The average amount of host write data in Mbytes that is passed through the SP per second.

LUN performance metrics

• Response Time (ms)

The average time, in milliseconds, that a request to a LUN is outstanding, including waiting time.

• Total Throughput (I/O/sec)

The average number of host requests that are passed through the LUN per second, including both read and write requests.

• Read Throughput (I/O/sec)

The average number of host read requests passed through the LUN per second.

• Write Throughput (I/O/sec)

The average number of host write requests passed through the LUN per second.

• Read Bandwidth (MB/s)

The average amount of host read data in Mbytes that is passed through the LUN per second.

• Write Bandwidth (MB/s)

The average amount of host write data in Mbytes that is passed through the LUN per second.

• Average Busy Queue Length

The average number of outstanding requests when the LUN was busy. This does not include idle time.

• Utilization (%)

The fraction of an observation period during which a LUN has any outstanding requests.

DISK performance metrics

• Utilization (%)

The percentage of time that the disk is servicing requests.

• Response Time (ms)

The average time, in milliseconds, that it takes for one request to pass through the disk, including any waiting time.

• Total Throughput (I/O/sec)

The average number of requests to the disk on a per second basis. Total throughput includes both read and write requests.

• Read Throughput (I/O/sec)

The average number of read requests to the disk per second.

• Write Throughput (I/O/sec)

The average number of write requests to the disk per second.

• Read Bandwidth (MB/s)

The average amount of data read from the disk in Mbytes per second.

• Write Bandwidth (MB/s)

The average amount of data written to the disk in Mbytes per second.

• Average Busy Queue Length

The average number of requests waiting at a busy disk to be serviced,

including the request that is currently in service.

CLARiiON SP, LUN and DISK performance data is retrieved and processed daily. Raw performance data is kept for a longer term, i.e. 180 days, and CLARiiON performance reports are kept indefinitely for performance trend analysis.