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OceanStor 18500 V3 and 18800 V3 Mission Critical Storage System V300R003 Basic Storage Service Guide for File 16

"This document describes the basic storage services and explains how to configure and managebasic storage services."

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Huawei uses machine translation combined with human proofreading to translate this document to different languages in order to help you better understand the content of this document. Note: Even the most advanced machine translation cannot match the quality of professional translators. Huawei shall not bear any responsibility for translation accuracy and it is recommended that you refer to the English document (a link for which has been provided).
Planning Disk Domains

Planning Disk Domains

A disk domain provides storage space for storage pools, whose storage tiers and available capacities depend on the disk types, capacity, and hot spare policy of the disk domain.

Encryption Types

Disks that comprise disk domains are divided into encrypted disks and unencrypted disks. Encrypted disks and unencrypted disks cannot coexist in one disk domain.

  • Encrypted disk: When data is written into or read from a disk, the data is encrypted or decrypted using the hardware circuit and internal encryption key of the disk. The encrypted disk is a special type of disk.

    Before using encrypted disks, install and configure the key management server, and complete its interconnection with the storage system. For details, see OceanStor 18500 V3&18800 V3 Mission Critical Storage System V300R003 Disk Encryption User Guide.

  • Unencrypted disk: Unencrypted disks are common disks that do not support the encryption function.

Planning Disk Types for a Disk Domain

A disk type in a disk domain corresponds to a storage tier of a storage pool. If the disk domain does not have a specific disk type, the corresponding storage tier cannot be created for a storage pool.

Table 2-4 describes the mapping between disk types and storage tiers.
Table 2-4  Mapping between disk types and storage tiers

Disk Type

Storage Tier

SSD

High performance tier

SAS disk

Performance tier

NL-SAS disk

Capacity tier

Planning Hot Spare Policies for a Disk Domain

To prevent data loss or performance deterioration caused by a member disk failure, the storage system employs hot spare space to take over data from the failed member disk.
  • If the product version is V300R003C00, the following hot spare policies are supported:
    • High

      The capacity of one disk is used as hot spare space if the number of disks at a storage tier equals to or fewer than 12. The hot spare space non-linearly increases as the number of disks increases. When the number of disks at a storage tier reaches 168, the storage tier uses the capacity of one disk in every 96 disks as the hot spare space.

    • Low

      The capacity of one disk is used as hot spare space if the number of disks at a storage tier equals to or fewer than 24. The hot spare space non-linearly increases as the number of disks increases. When the number of disks at a storage tier reaches 168, the storage tier uses the capacity of one disk in every 192 disks as the hot spare space.

    Table 2-5 describes how hot spare space changes with the number of disks. The hot spare space changes at a storage tier are used as an example here. The hot spare space changes at different types of storage tiers are the same.
    Table 2-5  Changes of hot spare space

    Number of Disks

    Number of Disks of Which Capacity Is Used as Hot Spare Space in High Hot Spare Policya

    Number of Disks of Which Capacity Is Used as Hot Spare Space in Low Hot Spare Policya

    (1, 12]

    1

    1

    (12, 24]

    2

    (24, 48]

    3

    2

    (48, 72]

    4

    (72, 120]

    5

    3

    (120, 168]

    6

    (168, 264]

    7

    4

    (264, 360]

    8

    a: Huawei storage systems use RAID 2.0+ virtualization technology. Hot spare capacity is provided by member disks in each disk domain. Therefore, the hot spare capacity is expressed in number of disks in this table.

    For example, if a disk domain is composed of 12 SSDs and the high hot spare policy is used, the hot spare space occupies the capacity of one SSD and the capacity is provided by member disks in the disk domain. If a disk domain is composed of 13 SSDs and the high hot spare policy is used, the hot spare space occupies the capacity of two SSDs.

    NOTE:
    • By default, the storage system uses the high hot spare policy. You can only run the change disk_domain general command on the CLI to modify the hot spare policy.
    • When you are creating a disk domain, ensure that the disks used to provide hot spare space are sufficient.
    • Hot spare space can be used for the current disk domain only.
    • Table 2-5 lists common capacity changes of the hot spare space. The number of disks supported by a storage system and the capacity of their hot spare space are based on actual specifications.
  • If the product version is V300R003C10 or V300R003C20, the following hot spare policies are supported:
    • High

      The capacity of one disk is used as hot spare space if the number of disks at a storage tier equals to or fewer than 12. The hot spare space non-linearly increases as the number of disks increases. When the number of disks at a storage tier reaches 175, the storage tier uses the capacity of one disk in every 100 disks as the hot spare space.

    • Low

      The capacity of one disk is used as hot spare space if the number of disks at a storage tier equals to or fewer than 25. The hot spare space non-linearly increases as the number of disks increases. When the number of disks at a storage tier reaches 175, the storage tier uses the capacity of one disk in every 200 disks as the hot spare space.

    Table 2-6 describes how hot spare space changes with the number of disks. The hot spare space changes at a storage tier are used as an example here. The hot spare space changes at different types of storage tiers are the same.
    Table 2-6  Changes of hot spare space

    Number of Disks

    Number of Disks of Which Capacity Is Used as Hot Spare Space in High Hot Spare Policya

    Number of Disks of Which Capacity Is Used as Hot Spare Space in Low Hot Spare Policya

    (1, 12]

    1

    1

    (12, 25]

    2

    (25, 50]

    3

    2

    (50, 75]

    4

    (75, 125]

    5

    3

    (125, 175]

    6

    (175, 275]

    7

    4

    (275, 375]

    8

    a: Huawei storage systems use RAID 2.0+ virtualization technology. Hot spare capacity is provided by member disks in each disk domain. Therefore, the hot spare capacity is expressed in number of disks in this table.

    For example, if a disk domain is composed of 12 SSDs and the high hot spare policy is used, the hot spare space occupies the capacity of one SSD and the capacity is provided by member disks in the disk domain. If a disk domain is composed of 13 SSDs and the high hot spare policy is used, the hot spare space occupies the capacity of two SSDs.

    NOTE:
    • By default, the storage system uses the high hot spare policy. You can only run the change disk_domain general command on the CLI to modify the hot spare policy.
    • When you are creating a disk domain, ensure that the disks used to provide hot spare space are sufficient.
    • Hot spare space can be used for the current disk domain only.
    • Table 2-6 lists common capacity changes of the hot spare space. The number of disks supported by a storage system and the capacity of their hot spare space are based on actual specifications.

Recommended Configurations for Disks in the Disk Domain

You are advised to configure a maximum of 100 disks for each tier in a disk domain. For example, if the number of disks on a tier is D (divide D by 100 and then round off the result to N and the remainder is M), you can refer to the following configurations:
  • If D ≤ 100, configure all disks on this tier in one disk domain.
  • If D > 100, create N+1 disk domains and evenly distribute all disks to the N+1 disk domains. That is, the number of disks in each disk domain is D/(N+1). In addition, it is recommended that disk enclosures be fully configured.
  • For SmartTier, it is recommended that a maximum of 100 disks be configured for each tier in a disk domain. The configuration of disks on each tier is the same as the preceding principle.

Example 1: The total number of SSDs in the storage system is 328, which is the value of D. (Divide 328 by 100. Round off the result to 3, which is the value of N. The remainder is 28, which is the value of M). You are advised to configure four disk domains, each of which contains 328/4 = 82 SSDs.

Example 2: If the total number of SSDs in the storage system is 223, which is the value of D. (Divide 223 by 100. Round off the result to 2, which is the value of N. The remainder is 23, which is the value of M). You are advised to configure three disk domains, each of which contains 223/3 = 74.3 disks. In this case, two disk domains are configured with 74 disks respectively and the other disk domain is configured with 75 disks.

Example 3: If a disk domain consists of SSDs, SAS disks, and NL-SAS disks, for SmartTier, the number of disks of each type cannot exceed 100.

NOTE:

If the project requires a disk domain containing over 100 disks to meet capacity and service planning requirements, contact Huawei technical engineers to evaluate.

Planning Capacity for a Disk Domain

The space of a storage pool originates from a disk domain. Therefore, the capacity of the disk domain determines the available capacity of the storage pool. The capacity of the disk domain must be properly planned to make full utilization of storage space. When planning the minimum capacity for a disk domain, you must set related parameters including the hot spare policy, RAID policy, and storage media to ensure that the disk domain can meet capacity requirements of storage pools and hot spare space. Table 2-7 describes the minimum number of disks required for planning a disk domain (for a single engine).

Table 2-7  Planning a disk domain (for a single engine)

RAID Policy

Minimum Number of Disks in a Disk Domain (SSD)

Minimum Number of Disks in a Disk Domain (SAS)

Minimum Number of Disks in a Disk Domain (NL-SAS)

RAID 0

6

8

8

RAID 1 (2D)

6

8

8

RAID 1 (4D)

6

8

8

RAID 10

6

8

8

RAID 3 (2D+1P)

6

8

8

RAID 3 (4D+1P)

6

8

8

RAID 3 (8D+1P)

10

10

10

RAID 5 (2D+1P)

6

8

8

RAID 5 (4D+1P)

6

8

8

RAID 5 (8D+1P)

10

10

10

RAID 6 (2D+2P)

6

8

8

RAID 6 (4D+2P)

7

8

8

RAID 6 (8D+2P)

11

11

11

RAID 6 (16D+2P)

19

19

19

RAID 50 (2D+1P)x2

7

8

8

RAID 50 (4D+1P)x2

11

11

11

RAID 50 (8D+1P)x2

19

19

19

NOTE:
  • The previous table only lists the minimum disk numbers required in standard RAID levels. In addition to that, the storage system also supports flexible configuration. For a flexibly configured RAID policy xD+yP, the minimum disk number is x+y+z when the number of required hot spare disks is z. The z value is determined by the hot spare policy and disk quantity.
  • The disks listed in the Minimum Number of Disks in a Disk Domain column of the preceding table must be provided by the same engine. If the disks that you use to create a disk domain are provided by different engines, ensure that the number of disks on each engine meets the disk number requirements (minimum number of disks).
Refer to the following suggestions to plan disk domains:
  • When creating a disk domain, manually select disks to ensure that all disks are from the same engine. Create disk domains on one engine to reduce the RAID failure probability and improve the read and write performance of RAID.
  • You are advised to use disks of the same type, capacity, and rotating speed (except SSDs) at the same storage tier in a disk domain. If disk capacities are not the same, disks with large capacities may not be used effectively or may become performance bottlenecks, wasting capacities. If disk rotating speeds are different, performance may deteriorate.
  • If both SAN and NAS services are deployed on a storage system, you are advised to create two disk domains, one for SAN services and the other for NAS services. If you want to configure both SAN and NAS services in one disk domain, contact Huawei technical support engineers to evaluate.
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Updated: 2019-08-14

Document ID: EDOC1000084081

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