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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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Planning Storage Pools

Planning Storage Pools

Before using a storage system, create storage pools to provide storage space for application servers, and make the following plans on the storage tiers, RAID levels, and hot spare policies based on your requirements.

Usage

Usage of a storage pool is unchangeable after it is configured. If Usage of a storage pool is set to Block Storage Service, the storage pool can only be used to create LUNs. If Usage of a storage pool is set to File Storage Service, the storage pool can only be used to create file systems. You are advised to use different disk domains to create storage pools for the block storage service and file storage service.

Storage Tiers

A storage pool is a logical combination of one or more storage tiers. The storage pool of the storage system supports a maximum of three storage tiers. A storage tier is a set of storage media that has the same performance and uses the same RAID level. Each storage tier provides different performance at different costs. You can configure storage tiers based on your requirements.

Table 2-8 lists the specifications of each storage tier.
Table 2-8  Specifications of each storage tier

Storage Tier

Storage Medium

Response Speed

Capacity Cost Per Gigabyte

Request Processing Cost Per Gigabyte

Tier 0 (high-performance tier)

SSD

Fast

High

High

Tier 1 (performance tier)

SAS

Medium

Medium

Medium

Tier 2 (capacity tier)

NL-SAS

Slow

Low

Low

Functions of different storage tiers are as follows:
  • High-performance tier: delivers the highest performance among the three tiers. As the cost of SSDs is high and the capacity of a single SSD is small, the high-performance tier is suitable for applications that require high random read/write performance, for example, database indexes.
  • Performance tier: delivers high-performance. As the cost of SAS disks is moderate and the capacity of a single SAS disk is large, the performance tier has good reliability and is suitable for general online applications.
  • Capacity tier: delivers the lowest performance among the three tiers. As the cost of NL-SAS disks is the lowest and the capacity of a single NL-SAS disk is large, the capacity tier is suitable for non-critical services, for example, backup.
Usage of a storage pool is unchangeable after it is configured. If Usage of a storage pool is set to Block Storage Service, the storage pool can only be used to create LUNs. If Usage of a storage pool is set to File Storage Service, the storage pool can only be used to create file systems.

RAID Levels

Consider the following when selecting RAID levels:
  • Reliability
  • Read/Write performance
  • Disk utilization
Different RAID levels provide different reliability, read/write performance, and disk utilization, as described in Table 2-9.
Table 2-9  RAID levels

RAID Level

Redundancy and Data Recovery Capability

Read Performance

Write Performance

Disk Utilization

Maximum Number of Allowed Faulty Disks

RAID 0

No data redundancy is provided and damaged data can not be recovered.

High

High

The disk utilization is 100%.

0

RAID 1

High. RAID 1 provides completely redundancy. When a CK fails, the mirror CK can be used for data recovery.

Relatively high

Relatively low

  • 2Da: The disk utilization is about 50%.
  • 4D: The disk utilization is about 25%.

A maximum of N-1 disks can fail at the same time (in a RAID 1 disk array with N disks).

RAID 3

Relatively high. Each CKG has one CK as the parity CK. Data on any data CK can be recovered using the parity CK. If two or more CKs fail, the RAID level fails.

High

Low

RAID 3 supports flexible configurations. Specifically, a RAID 3 policy allows data block and parity block policies ranging from 2D+1P to 13D+1P. The following examples show disk utilization rates of several configurations commonly used by RAID 3:
  • 4D + 1Pb: The disk utilization is about 80%.
  • 2D + 1P: The disk utilization is about 66.67%.
  • 8D + 1P: The disk utilization is about 88.89%.

1

RAID 5

Relatively high. The parity data is distributed on different CKs. In each CKG, the parity data occupies space of a CK. RAID 5 allows the failure of only one CK. If two or more CKs fail, the RAID level fails.

Relatively high

Relatively high

RAID 5 supports flexible configurations. Specifically, a RAID 5 policy allows data block and parity block policies ranging from 2D+1P to 13D+1P. The following examples show disk utilization rates of several configurations commonly used by RAID 5:
  • 2D + 1P: The disk utilization is about 66.67%.
  • 4D + 1P: The disk utilization is about 80%.
  • 8D + 1P: The disk utilization is about 88.89%.

1

RAID 6

Relatively high. Two groups of parity data are distributed on different CKs. In each CKG, the parity data occupies space of two CKs. RAID 6 allows two CKs to fail simultaneously. If three or more CKs fail, the RAID level fails.

Medium

Medium

RAID 6 supports flexible configurations. Specifically, a RAID 6 policy allows data block and parity block policies ranging from 2D+2P to 26D+2P. The following examples show disk utilization rates of several configurations commonly used by RAID 6:
  • 2D + 2P: The disk utilization is about 50%.
  • 4D + 2P: The disk utilization is about 66.67%.
  • 8D + 2P: The disk utilization is about 80%.
  • 16D + 2P: The disk utilization is about 88.89%.

2

RAID 10

High. RAID 10 allows multiple CKs to fail simultaneously. When a CK fails, the mirror CK can be used for data recovery. If a CK and its mirror CK fail simultaneously, the RAID level fails.

Relatively high

Relatively high

The disk utilization is 50%.

A maximum of N disks can fail at the same time (in a RAID 10 disk array with 2N disks).

RAID 50

Relatively high. The parity data is distributed on different CKs of each RAID 5 sub-group. In each RAID 5 sub-group, only one CK is allowed to fail. If two or more CKs of a RAID 5 sub-group fail simultaneously, the RAID level fails.

Relatively high

Relatively high

  • (2D + 1P) x 2: The disk utilization is about 66.67%.
  • (4D + 1P) x 2: The disk utilization is about 80%.
  • (8D + 1P) x 2: The disk utilization is about 88.89%.

1

a: D indicates the data block.

b: P indicates the parity block.

NOTE:

For a flexibly configured RAID policy xD+yP, the disk utilization is [x/(x + y)] × 100%.

You can configure RAID policies according to the following rules:
  • For critical service systems, such as billing systems of operators and class-A financial online transaction systems, you are advised to configure RAID 6 (8D+2P) for the performance tier. For non-critical service systems, you are advised to configure RAID 5 (8D+1P) for the performance tier.
  • You are advised to configure RAID 6 for the capacity tier (NL-SAS).
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Updated: 2019-08-14

Document ID: EDOC1000084081

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