This article describes how to use the Solutions Enabler command symstat to view the performance statistics of Symmetrix Array. The symstatcommand captures, in real-time, statistics information about a Symmetrix array.

The symstat command performs the following features:

• Retrieves the performance counts for the Symmetrix array as a whole
• Retrieves the performance counts for a Director or Director Ports
• Retrieves the performance counts for Symmetrix devices
• Retrieves the performance counts for Device Group, Composite Group, RDF Group

The symstat command provides different types of performance display options:

• REQUESTS - Reports I/O requests and throughput for selected devices, directors, or SRDF/A sessions. (This is the default type; if no type is specified, REQUESTS is used.)
• BACKEND - Reports back-end I/O requests and throughput for selected devices.
• PORT - Reports performance statistics for a director port.
• ISCSI - Reports GigE network statistics.
• CACHE - Reports cache activity for selected front-end or remote link directors, or SRDF/A sessions
• MEMIO - Reports cache memory to disk activity for selected devices.
• CYCLE - Reports cycle summary information for SRDF-A sessions
• DISK - Reports back-end I/O requests and throughput for selected disks.
• PREFETCH - Reports track prefetch disk activity for selected back-end directors only.
• RDF - Reports SRDF statistics from the perspective of RA groups, devices, or directors.
• DMSP - Reports dynamic mirroring service policy (DMSP) statistics for the selected device(s).

Command Examples:

1. Array Performance Statistics. I/O and throughput statistics can be returned for all devices on a specific array by specifying the Symmetrix ID by -sid, specifying the interval by –iand the number of samples (counts) by –C. ( Symmetrix ID = 250, counts = 100, interval = 60 in following example)

symstat-type REQUEST -sid 250 -i60 -c 100

In command output, IO/Sec READ/WRITE are Read/Write IOPS, KB/Sec READ/WRITE are Throughput per second.

2. Device Performance Statistics. symstat can display performance statistics such as I/O requests via front-end adapters and throughput on devices. For example, for sample intervals of 120 seconds and a sample count of 3 on logical device DEV001 in device group prod_r1, use command:

symstat -i 250 -c 3 -g prod_r1 -ld DEV001

3. Device BACKEND Statistics. Using symstat with the BACKEND type specified,you can display performance statistics such as I/O requests using a DA (back-end director) and throughput on a device.

symstat-type BACKEND -i 60 -c 3 -g prod_r1 -ld DEV001

4. Director I/O requests. symstat can display the I/O requests and throughput activity performance statistics on any or all directors.

symstat-type REQUESTS -sid 250 -dir ALL -i60 -c 100

Specifying single director, use following command:

symstat-type REQUESTS -dir 7b -sid 250 -i10 -c 100

In command output, IO/sec is IOPS which summarize Host to Front-end directors, disk to Back-end directors, local to Remote link directors. RW is Total read/write cache request rate.

5. Director ports performance statistics. Using symstat with the PORT type specified, you can display performance statistics such as I/O requests (IO/Sec) and throughput (Kbytes/Sec) of director ports for a specific Symmetrix array. For example, for sample intervals of 60 seconds, and a sample count of 3 (for I/O requests and throughput) on Symmetrix 250 all director ports:

symstat -i 60 -c 5 -type PORT -sid 250 -dir ALL

Specifying single director port, use following command:

symstat-type REQUESTS -dir 7b -sid 250 -i10 -c 100

6. MEMIO performance statistics. Using symstat, you can display performance statistics, such as cache memory to disk I/O on particular device group. For example, enter

symstat-type MEMIO -sid 250 -i 60 -c 100

In command output, WP Tracks are the count not yet destaged to disk. Prefchd/DestgdTracks/SecareTracks per second pre-fetched from disk to cache upon detection of a sequential read stream and

Tracks per second saved into disks. %Dev WPmax is Write-pending device limit percentage which defined on VMAX system level.

7. Disk performance statistics. Using symstat with the DISK type specified,you can display performance statistics, such as I/O requests and throughput on a physical disk. For example, for sample intervals of 60 seconds and a sample count of 3 on disk 02A:C5, enter:

symstat-type disk -i 60 -c 3 -sid250 -disk 2a,C,5

For all SCSI IDs on DA 02A, interface C, use command:

symstat-type disk -i 60 -c 3 -sid250 -disk 2a,C,ALL

8. SRDF performance statistics. The SRDF type statistics extend the statistical information provided by the SRDF director to external applications providing greater visibility into the performance and behavior of Symmetrix arrays in the field. These statistics can be used to monitor on-going activity and to analyze problematic behavior.

To return statistics for all RA group numbers, specify all, use command:

symstat -sid 250 -i 60 -c 2 -type RDF -rdfg 11

For example, to return SRDF device-level statistics for device 37, use command:

symstat -sid 250 -i 60 -c 2 -type RDF -dev 37

To return SRDF director level statistics, use command:

symstat -sid 250 -i 60 -c 2 -type RDF -dir 1d

To return link-level details, specify the -rdflink option as shown in the example below command.

symstat -sid 250 -i 60 -c 2 -type RDF -dir 2c –rdflink

For more command symstatcommand example, you can refer EMC Solutions Enabler Symmetrix Array Management CLI Product Guide on support.emc.com

Author: Fenglin Li

iEMC APJ

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