What is RAID?
RAID (Redundant Array of Independent Disks) is a data storage technology that allows multiple hard drives to be combined into a single storage unit. Data is distributed across the drives in one of several ways or RAID levels," depending on the level of redundancy and performance required. RAID levels are not ratings, but rather classifications of functionality. Different RAID levels offer dramatic differences in performance, data availability, and data integrity depending on the specific I/O environment. There is no single RAID level that is perfect for all users.
RAID Type and Application
There are number of things that need to be considered when choosing a RAID solution：
- Performance and Application Requirements：Read and write performance, failure tolerance, and data redundancy are the main factors to consider when selecting the right RAID solution for your application. (See Table 1)
- Hard Disk Drive Capacity and RAID Card Scalability：Some RAID cards can connect up to 256 SAS/SATA hard drives while others can only connect to 4. The number of HDDs to be used in a RAID solution and how much disk space needed for future storage are two main decision points to consider in selecting RAID card.
- Cache Protection：Cache protection protects cache memory on the RAID card by using an additional battery pack. Only certain RAID cards support cache protection. For companies that cannot afford data loss due to a power outage, cache protection on the RAID card is a must.
- Cost Concern：Cost is always associated with performance. For some corporations, performance is a bigger concern than cost. But when cost is a concern, learning to balance cost vs. performance during implementation of a RAID solution, will be very critical.
Table 1
| RAID Level |
1 |
5 |
10 |
| Fault Tolerance |
Yes |
Yes |
Yes |
| Physical Drive Capacity Utilization |
50% |
67% |
50% |
| Read Performance |
Very High |
Superior |
Very High |
| Write Performance |
Very High |
High |
Very High |
| Minimum Number of Drives |
2 |
3 |
4 |
| Applications |
Simple system backup and data protection |
- General purpose file servers
- Database Applications
|
High performance and systems requiring high reliability |
| Picture |
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