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.

1. Log into Connectrix Manager using the Username and password that was provided by the Customer. Note that the default username and password is Administrator and password.

2. You should now be in Product view. From Product view, double click on the switch Icon.

3. You should now be in Hardware view. From Hardware view, move the mouse pointer over the Maintenance Icon and select the data collection option. In version 6.0 and above, you need to select the maintenance pull down menu and select data collection.

4. This will bring up the Save Data Collection dialog box. Type the name that you would like to save the data collection as in the File Name: text box. We recommend that you save it in the format of Customername_switchname_date.zip (i.e.. enron_sw01_08082002.zip). In what directory it is saved in is unimportant as long as you remember where it is.

5. Take the zip disk currently in the zip drive out of the zip drive and replace it with the one that came with the replacement part.

6. Move the data collection file to the zip disk (cut or copy and paste).

7. Take the zip disk containing the data collection out of the zip drive and replace it with the one that was originally in there.

8. Include the zip disk containing the data collection with the part being returned.

Gold Copy represents a virtual point-in-time copy of the secondary LUN before the secondary LUN is updated with the changes from the primary LUN. Since it is a pointer-based virtual copy it only consumes space in the reserved LUN pool based on the amount of changes on the secondary LUN. During the secondary LUN update, the Gold Copy tracks all of the updates. When a region on the secondary is updated, the original region is copied to the reserved LUN pool to preserve a consistent point-in-time view of the secondary LUN at the time of start of update. This is a key feature that always ensures a consistent view of the secondary LUN. If the update from primary to secondary is interrupted due to a link failure or due to failure at the primary site (during the update), the Gold Copy is used by MirrorView/A software to rollback the partial update on the secondary LUN and return it to its previous consistent state.

Delta Set : MirrorView uses asynchronous writes, which means that I/O is not sent to the remote site at the same time as the host I/O. It is a periodic replication of a set of LUNs to a remote storage system. The Delta Set is created and changes are tracked during a MirrorView/A replication cycle. MirrorView/A replicates only

the last changed blocks during replication cycle and results in lower bandwidth requirement than synchronous or traditional native ordered write techniques. The Delta Set is, in reality, a local snap taken at the source side at the time of replication.