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Basic Storage Service Configuration Guide for Block

OceanStor V5 Series V500R007

This document is applicable to OceanStor 5110 V5, 5300 V5, 5500 V5, 5600 V5, 5800 V5, 6800 V5, 5300F V5, 5500F V5, 5600F V5, 5800F V5, 6800F V5, 18500 V5, 18800 V5, 18500F V5, and 18800F V5. It describes the basic storage services and explains how to configure and manage them.
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Modifying the Advanced Properties of a LUN (Applicable to V500R007C30 and Earlier)

Modifying the Advanced Properties of a LUN (Applicable to V500R007C30 and Earlier)

This operation enables you to modify the advanced properties of a LUN, such as the prefetch policy and cache policy.

Prerequisites

At least one LUN has been created.

Procedure

  1. Log in to DeviceManager.
  2. Choose Provisioning > LUN.
  3. Select the LUN whose properties you want to modify and click Properties.

    The Properties of LUN dialog box is displayed.

  4. Choose More > Advanced and modify the desired properties.

    Table 6-10 lists related parameters.
    NOTE:

    For a PE LUN, you can only modify its owning controller.

    Table 6-10 Advanced properties of a LUN

    Parameter

    Description

    Setting

    Owning Controller

    Owning controller of a LUN. You are advised to allocate LUNs to both controllers for load balancing.

    Select an owning controller based on the site requirements.

    NOTE:

    For a four-controller storage system, after a LUN is created, its owning controller can switch between only paired controllers, that is, between controller A and controller B, or between controller C and controller D.

    For example, if you select CTE0.A as the owning controller when creating a LUN, you can select only CTE0.A or CTE0.B as LUN's owning controller when modifying the LUN's advanced properties.

    Working Controller

    Working controller of a LUN, which is the only controller that processes read/write requests on the LUN. If hosts send I/Os to a non-working controller, the I/Os are forwarded to the working controller for processing.

    [Example]

    CTE0.A

    Read Policy

    Data read policy of a cache.

    The system supports the following read policies.

    • Resident: suitable for random access. The storage system caches data as long as possible to improve the read hit ratio.
    • Default: suitable for common access. The storage system strikes a balance between the read hit ratio and disk access performance.
    • Recycle: suitable for sequential access. The storage system releases idle cache resources as soon as possible for other services to use.

    [Example]

    Recycle

    [Default value]

    Default

    Write Policy

    Data write policy of a cache.

    The system supports the following write policies.

    • Resident: suitable for random access. The storage system caches data as long as possible to improve the write hit ratio.
    • Default: suitable for common access. The storage system strikes a balance between the write hit ratio and disk access performance.
    • Recycle: suitable for sequential access. The storage system releases idle cache resources as soon as possible for other services to use.

    [Example]

    Recycle

    [Default value]

    Default

    Prefetch Policy

    Read mode of a LUN. When reading data, the storage system prefetches required data from disks to the cache in advance according to a preset policy. The system supports the following prefetch policies:

    • No prefetch: The storage system reads data based on the read length specified in the I/O request.

      As a low read hit ratio may lead to performance degradation, No prefetch is recommended for random read services.

    • Intelligent prefetch: The storage system analyzes the continuity of read requests from hosts. If the read requests are continuous, the data following the current read request is prefetched from disks to the cache. In this way, the cache hit ratio can be increased. If the requests are random reads, the data is read directly from disks.
    • Constant prefetch: A constant length of data is read from disks each time when the cache reads data from the disks. The length is user-defined, ranging from 0 to 1024 KB.
    • Variable prefetch: The cache reads data from disks based on a multiple of the read length specified in the I/O request. The multiple is user-defined, ranging from 0 to 1024.

    [Example]

    Intelligent prefetch

    Thin LUN Alarm Threshold

    This parameter is valid only when the selected LUN is a thin LUN and the operating system of the application server that accesses the LUN is Windows Server 2012.

    Once this parameter is enabled, the application server will receive a threshold alarm when the percentage of the LUN's used capacity to its total capacity exceeds the configured Alarm Threshold (%).

    [Value range]

    50 to 99

    [Default value]

    90

    LUN Write Policy

    The LUN write policy can be:

    • Write back: Data is written onto the cache. The cache schedules the data and writes the data to disks.
    • Write through: Data is directly written onto disks without passing the cache.
    NOTE:

    Writing data onto the cache is fast. Therefore, write back delivers better write performance than write through.

    [Example]

    Write back

    [Default value]

    • eDevLUN: write through.
    • Local LUN: write back.
    NOTE:

    After a masqueraded eDevLUN is created, you are not allowed to modify its LUN write policy. You can modify the policy after you manually take over the masqueraded eDevLUN through the CLI.

    Masquerading

    Masquerading replaces the identification information of local LUNs with that of heterogeneous remote LUNs to take over heterogeneous remote LUNs online.

    Masquerading types can be:

    • No masquerading
    • Basic masquerading

      Applies to eDevLUNs, used for replacing the basic LUN information such as the VID, PID, and LUN WWN.

    • Extended masquerading

      Applies to eDevLUNs, used for replacing the basic LUN information and extended LUN information such as the SCSI protocol version, owning controller, and working controller.

    • Inherited masquerading

      Applies to local LUNs, used for inheriting the remote LUN information such as the VID, PID, and SCSI protocol version.

    • Third-party

      Applies to eDevLUNs, used for taking over heterogeneous storage systems from third-party vendors online.

    [Example]

    Inherited masquerading

    [Default value]

    No masquerading

    NOTE:
    • The selection of basic masquerading or extended masquerading depends on the vendor and version of the multipathing software and the versions of Huawei heterogeneous storage systems. For recommended parameter settings in different scenarios, see the SmartVirtualization feature guide specific to your product model.
    • If you select Inherited masquerading, Remote Device must be specified.
    • The masquerading type of LUNs that have been mapped to hosts cannot be changed.
    • If you want to change the masquerading type, change the current masquerading type to No masquerading and change the type.

    Takeover LUN WWN

    WWN of the eDevLUN after takeover.

    [Example]

    -

  5. Confirm the configuration of the advanced properties of a LUN.

    1. Click OK.

      The Execution Result dialog box is displayed, indicating that the operation succeeded.

    2. Click Close.

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Updated: 2019-08-30

Document ID: EDOC1000181506

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