Planning Storage Pools
This section describes how to plan storage pools, including their usage, storage tiers, and RAID levels.
Planning Usage
- Usage of a storage pool is unchangeable after being 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 and file storage services.
Planning Storage Tiers
A storage pool is a logical combination of one or more storage tiers. A storage pool 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. Various storage tiers provide different performance at different costs.
Table 4-7 lists the specifications of each storage tier.
Storage Tier |
Storage Medium |
Response Speed |
Per-GB Cost |
Per-I/O Cost |
|---|---|---|---|---|
High-performance tier |
SSD |
Fast |
High |
High |
Performance tier |
SAS disk |
Medium |
Medium |
Medium |
Capacity tier |
NL-SAS disk |
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 common 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.
Planning RAID Levels
Different storage tiers may have different RAID policies. Consider the following requirements 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 4-8 and Table 4-9.
RAID Level |
Redundancy and Data Recovery Capability |
Read Performance |
Write Performance |
Maximum Number of Allowed Faulty Disks |
|---|---|---|---|---|
RAID 0 |
No data redundancy is provided and corrupted data cannot be recovered. |
High |
High |
0 |
RAID 1 |
2Da: relatively high 4D: high RAID 1 provides complete redundancy. If a CK fails, the mirror CK can be used to recover the data. |
Relatively high |
Relatively low |
NOTE:
With both data and mirroring chunks, the system delivers the best reliability performance, that is, can tolerate the concurrent failure of the most disks, in either of the following scenarios:
With both data and mirroring chunks, the system delivers the worst reliability performance, that is, can tolerate the concurrent failure of the fewest disks when a data chunk and all its mirroring chunks are faulty. |
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, RAID 3 protection can no longer be provided. |
High |
Low |
1 |
RAID 5 |
Relatively high. 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, RAID 5 protection can no longer be provided. |
Relatively high |
Relatively high |
1 |
RAID 6 |
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, RAID 6 protection can no longer be provided. |
Medium |
Medium |
2 |
RAID 10 |
Relatively high. RAID 10 allows multiple CKs to fail simultaneously. If a CK fails, the mirror CK can be used to recover the data. If a CK and its mirror CK fail simultaneously, RAID 10 protection can no longer be provided. |
Relatively high |
Relatively high |
NOTE:
With both data and mirroring chunks, the system delivers the best reliability performance, that is, can tolerate the concurrent failure of the most disks, in either of the following scenarios:
With both data and mirroring chunks, the system delivers the worst reliability performance, that is, can tolerate the concurrent failure of the fewest disks when a data chunk and its mirroring chunks are faulty. |
RAID 50 |
Relatively high. 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, RAID 50 protection can no longer be provided. |
Relatively high |
Relatively high |
1 |
a: D indicates a data block. |
||||
RAID Level |
Typical Disk Utilization |
|---|---|
RAID 0 |
100% |
RAID 1 |
|
RAID 3 |
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 of several configurations commonly used by RAID 3:
|
RAID 5 |
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 of several configurations commonly used by RAID 5:
|
RAID 6 |
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 of several configurations commonly used by RAID 6:
|
RAID 10 |
50% |
RAID 50 |
|
a: D indicates a data block. b: P indicates a parity block. NOTE:
|
|
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 disks).
Planning Whether to Use the Enhanced RAID Data Protection Policy
When creating a storage pool, you can select whether to use the enhanced RAID data protection policy. If the enhanced RAID data protection policy is used, the storage system will evaluate whether the current data reliability meets the recommended requirements based on the disk type, disk quantity, single disk capacity, RAID level, and RAID member disk quantity in the current disk domain.
- For versions earlier than V500R007C70:
- If the current data reliability meets the recommended requirements, you can create a storage pool successfully.
- If the current data reliability does not meet the recommended requirements, you are not allowed to create a storage pool using the current configurations. In this case, you can adjust the RAID policy or create a disk domain that contains the required number of same-type disks so that the data reliability meets the recommended requirements.
Example: A disk domain consists of 70 SAS disks with an average capacity of 1200 GB per disk. Creating a RAID 5 (8D+1P) storage pool in this disk domain will fail because the number of SAS disks exceeds the recommended value for recommended data reliability. You are advised to create a disk domain that contains fewer (for example 65) SAS disks, or adjust the RAID policy of the storage pool, for example, to RAID 5 (7D+1P).
- For V500R007C70 and later versions: The storage system automatically filters out RAID policies that do not meet the recommended data reliability requirements.
- For details about how a storage system evaluates whether the recommended data reliability requirements are met, see https://forum.huawei.com/enterprise/en/criteria-to-evaluate-whether-recommended-data-reliability-requirements-are-met-with-enhanced-data-protection-policy-used/thread/396345-891.
- Data reliability is evaluated by calculating the probability that data will not be lost if multiple disks in a disk domain fail at the same time.
- The GUI may vary with the product version. The actual GUI prevails. For versions earlier than V500R007C70, this function is displayed as Use the enhanced data protection policy.
