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Performance Monitoring Guide

OceanStor Dorado V3 Series V300R002

This document describes performance monitoring of storage systems, including the monitoring method, indicator planning, configuration monitoring, and problem diagnosis.
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Understanding the Performance of Back-End Ports and Disks

Understanding the Performance of Back-End Ports and Disks

Information on back-end ports, disks and how they affect performance helps in the identification and location of problems in the storage system.

Analyzing the Performance of Back-End Ports

Back-end ports refer to SAS ports that are used to connect a controller to a disk enclosure and provide a channel for reading and writing data to disks. The impact of these typically lie in a disk enclosure loop and affects performance. The storage systems support 12 Gbit/s SAS ports.

The bandwidth of a single SAS port is limited. Therefore, ensure that the bandwidth supported by SAS ports in a loop is higher than that of all disks in the disk enclosures. In addition, as the number of disk enclosures in a loop becomes larger, the latency caused by expansion links is longer. As a result, the back-end I/O latency is affected, thereby affecting the IOPS. Considering the preceding situations, when there are sufficient SAS ports, the following methods are recommended:

  • Distribute disk enclosures to multiple loops.
  • If a single controller has multiple back-end interface modules, distribute the loops to multiple modules instead of using the SAS ports on one module.
  • Form a loop using less than five disk enclosures.

You can use OceanStor DeviceManager or CLI to query the disk enclosure IDs and then determine loop connections. The ID of a disk enclosure is in the format of DAEabc (a, b, and c are integers), where a indicates the engine ID, b indicates the loop ID, and c indicates the ID of an enclosure in the loop. For example, the disk enclosure IDs are DAE000, DAE010, DAE020, DAE021, DAE030, and DAE031. The IDs indicate that there are two 2-enclosure loops (DAE020 and DAE021 compose one loop; DAE030 and DAE031 compose another) and two single-enclosure loops (DAE000; DAE010). The loop connections comply with the preceding performance rules.

To view the performance indicators including the port usage rate, total IOPS, and block bandwidth, use OceanStor DeviceManager or SystemReporter, or run the CLI command.


Performance indicators of back-end ports vary with different versions. The actual interface prevails.

  • Use OceanStor DeviceManager to view the indicators. Operation path: Monitor > Performance Monitoring > Back-End Port.

  • Use SystemReporter to view the indicators. Operation path: Monitoring > Real-time Monitor > Back-End Port.

  • Run show performance port on the CLI to view the indicators.
    admin:/>show performance port port_id=CTE0.A0.P1 
    0.Bandwidth(MB/s) / Block Bandwidth(MB/s)     
    2.Read Bandwidth(MB/s)                        
    3.Read Throughput(IOPS)(IO/s) 
    4.Write Bandwidth(MB/s)                       
    5.Write Throughput(IOPS)(IO/s)                
    6.Average I/O Latency(ms)                     
    7.Max. I/O Latency(ms) 
    8.Max Read I/O Latency(ms)                    
    9.Max Write I/O Latency(ms)                   
    10.Average Read I/O Latency(ms)               
    11.Average Write I/O Latency(ms) 
    12.Average I/O Latency(us)                    
    13.Max. I/O Latency(us)                       
    14.Max Read I/O Latency(us)                   
    15.Max Write I/O Latency(us) 
    16.Average Read I/O Latency(us)               
    17.Average Write I/O Latency(us) 
    Input item(s) number seperated by comma:

Rules of Selecting Disks for a Disk Domain

The selection of disks for a disk domain affects the performance of a storage system.

To ensure high performance, observe the following rules:

  • Do not adopt dual-controller access in a bandwidth-sensitive scenario.

    To ensure high reliability, a dual-controller access system is set up whereby both controllers A and B can deliver I/Os to disks in a disk domain simultaneously. This is done by having each disk enclosure loop connected to a SAS port on controllers A and B, separately but simultaneously. In contrast, single-controller access has only one controller that delivers I/Os to disks. However, dual-controller access affects the sequence of I/Os which makes it deliver a lower bandwidth performance compared to that of a single-controller. Therefore, for services which require high bandwidth, such as M&E industry outputs, a single-controller access set up would be more ideal. For services that involve random I/Os, adopting dual-controller access would be more appropriate.

  • Do not select disks across engines.

    Selecting disks across engines affect the latency and bandwidth performance. This is because I/Os are forwarded through switching channels between engines. Therefore it is best to avoid this option when disks are sufficient. It is recommended that you select disks from the same disk enclosure.

  • Do not intermix different types of disks.

    In a RAID scenario, low performing disks may limit the overall performance of a stripe group. This is because disks of different rotational speeds and capacities vary in I/O processing latency and bandwidth. In addition, fast and slow disks may coexist, and they may be used unevenly. If disks are sufficient, select disks of the same rotational speed and capacity for a disk domain. Avoid intermixing different disk types.

    To query if a domain's disks are of the same type and capacity, use OceanStor DeviceManager.

Analyzing the Disk Performance

Storage media supported by OceanStor Dorado V3 storage systems are SSDs. When making a storage plan, you need to know SSD performance.

SSDs have greater advantages over HDDs in terms of I/O models with hotspot data access and sensitivity to response latency. In particular, this is the case with random small I/O read models of database applications. SSDs do not have the spin latency that can be seen in HDDs. In bandwidth-sensitive applications, SSDs slightly outperform HDDs. In the tiered storage technology, SSDs are used to compose the high-performance tier required for high IOPS pressure.

If a performance problem occurs and the front end of the storage system is normal, check whether disks have reached the performance threshold. If this is the case (the disk utility level has reached almost 100%), then there is a restriction issue with the back-end disk performance as the IOPS and bandwidth cannot increase. To query disk utilization levels, use SystemReporter.

To ensure the reliability and full service life of a disk, keep utility below 70% as recommended. For high capacity purposes (above 90% utilization needs), it is recommended that you add disks to the domain or migrate services to disks that provide higher performance.

Updated: 2019-07-17

Document ID: EDOC1100049152

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