About SAN-storage RAID group and RAID level settings & lt; some minor suggestions & gt;

In recent years, customers have always asked original storage engineers about the storage RAID plan (RAID, 5, 6 ....): "How many RAID are used? What RAID level is used? Why is RAID at this level used? What are the benefits of this level? Wait, "the storage engineer may be tired of repeating the problem, or it may be just a short time before the entry. It is always a simple summary:" RAID 5, low capacity loss, the speed is also slow ". As a result, the resource-LUN required by my projects in recent years is a rack cabinet and a RAID 5.

Frankly speaking, in previous projects, these are not my responsibilities, so I will keep my opinions, but I will always think about this: in the face of the immature voice of the customer, you can reply in five sentences, 50 sentences, or even the whole morning. However, as customers, they have sufficient rights to understand product information, even if they are unable to comprehend more in-depth technical details due to lack of experience, they also have the right to know. It is not complicated to describe the technical details, right?

If we treat it as a way to favor customers, relieve the pressure on sales colleagues, or make other RAID levels () feel a little bit confident, why not? Pai_^

However, we only need to establish some logic on the content of the explanation!

(* Although the content is marked as original, it is not the result of the analysis by the people, but some suggestions from the headquarters Technical Support. I just translated it according to the reading habits of Chinese people, add some of your own experience and hope you can use better logic to describe the customer or use more practical experience !!!)

 

The following figure shows the advantages and disadvantages of each RAID level. Some key data can be stored in the solution to improve the overall authority of the solution.

• Disk Type and Performance

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These suggestions help us purchase disks with specific features based on budget and performance requirements. However, these are all theoretical values, and the actual results may be different, because the vendor often hides the Head Positioning time, random access response, and the performance degrades after the disk is used to 70%.

 

• Strip size and Performance

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If you have a chance to select 2 TB capacity, what is the difference between choosing 3 GB disks and 15 GB disks? Of course, the latter will occupy more disk positions and budgets, but it has improved performance by 15 times (IOPs ).

• RAID settings

In fact, in terms of technology, different RAID levels are not only high and low capacity loss, but also low performance. In addition, RAID reconstruction is often ignored. If the reconstruction cycle is longer, this is a more serious risk. How many situations in our past environment allow users to store two disks in one hour at the same time?

This is the best practice to map disks and RAID levels with different features to different types of businesses, as shown in the suggestions (discussed later on the RAID level ):

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I. What is the rational use of RAID groups and RAID levels? The core content of this issue is as follows (in large and medium-sized IT environments ):

1. Create a RAID group for 15 disks and Output a lun:

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Excellent: IO is distributed across multiple disks, with high performance. Minimized resource overhead (depending on the RAID level ).

Poor: If a RAID fails, the entire RAID group will become invalid. The RAID reconstruction process is long and the performance will decrease. IO writes to the disk through a LUN spindle, and data concurrency may cause bottlenecks.

2. Create a RAID group for 15 disks and output 3 Luns:

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Excellent: minimum resource overhead (depending on the RAID level );

Poor: If a RAID fails, the entire RAID group will be rebuilt. RAID group reconstruction takes a long period of time, resulting in performance degradation;

<Poor performance and many disadvantages. We do not recommend this configuration.>

3. 15 disks are in three RAID groups, and one LUN is output for each RAID group:

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Excellent: Three I/O queues are available for storage; distributed read/write and performance improvement; a RAID failure only affects one LUN; RAID reconstruction can be quickly restored.

Poor: higher storage overhead (depending on the RAID level ).

<More advantages than disadvantages. Balance performance/availability and cost. Recommended configuration.>

4. No RAID level is specified. All disks are output independently (JBoD)

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Excellent: no capacity loss; multiple I/O extensions to disks; distributed read/write disks;

Poor: there is no security mechanism to protect;

 

 

2. What is the rational use of RAID groups and RAID levels?

RAID 0

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Excellent: Make full use of resources; Highest Write Performance; Highest read performance;

Poor: Potential high risk; IO writing from a LUN to a queue may block high concurrency of data; failure of a single disk may cause damage to the entire LUN; RAID reconstruction may take a long period of time.

<Worse than better, please avoid this setting as much as possible>

RAID 1

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Excellent: high security level; high-sequential read/write performance; high-random read/write performance; load balancing for all Luns; RAID faults do not significantly affect performance; RAID reconstruction can be quickly restored.

Poor: 50% capacity loss.

<A large number of I/O operations can be read and written through multiple LUN spindle, and RAID reconstruction can be achieved quickly, reducing the risk of faults. Significant advantages for High-concurrency random data I/O read/write>

RAID 10

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Excellent: high security level; high-sequential read/write performance; high-random read/write performance;

Poor: 50% capacity loss; less IO queues, compared with Raid 1.

<RAID 10 has no significant advantages. For special business models (such as a large number of sequential reads and writes), it will benefit from the bottom-layer strip settings, multiple RAID 1 sets have more advantages than RAID 10 in access (for example, more IO queues)>

RAID 5

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Excellent: moderate capacity loss; high-sequential read/write performance; high-random read performance;

Poor: Low-random Write Performance; medium security level; RAID reconstruction affects performance.

<RAID 5 settings can be improved-sequential read/write and random read. Due to the working mechanism, the verification information needs to be re-calculated and updated, and high-concurrency random writes may be affected by performance. Disk failure causes RAID reconstruction, which significantly reduces the performance. RAID 5 is suitable for the primary sequential IO read/write or high random read. Such as file servers and server Load balancer databases. We recommend that you create multiple RAID 5 subsets>

 

We hope that this content can be used as a basis in practice, regardless of communication with the customer or operation deployment.

Related suggestions are for reference only !!!

The End ...............

Thanks.

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