Disk striping, also known as RAID 0, is a type of RAID (Redundant Array of Independent Disks) that spreads data across multiple disk drives. The main benefit of disk striping is improved performance since data can be read and written simultaneously from multiple disks. However, RAID 0 provides no redundancy or fault tolerance.
What is Disk Striping?
Disk striping, as the name suggests, stripes data across multiple disk drives. The data is divided into blocks and distributed in stripes across the disks in the array. For example, in a 2 disk RAID 0 array, the first block of data would be written to disk 1, the second block to disk 2, the third block to disk 1 again, and so on. This allows reads and writes to occur in parallel, improving overall performance.
Some key characteristics of disk striping:
- Data is striped in blocks across multiple drives
- Reads and writes can occur in parallel, improving performance
- There is no parity or redundancy, so the failure of one disk causes complete data loss
- At least 2 disks are required for RAID 0
- The storage capacity equals the sum of the capacities of each disk
- RAID 0 provides the best performance of all RAID levels but no fault tolerance
Advantages of Disk Striping
There are several notable benefits to using disk striping in RAID 0:
- Increased performance – By striping data across multiple disks, read and write operations can occur simultaneously on different disks for improved performance. This makes RAID 0 well-suited for applications that demand high speed such as video editing or gaming.
- High throughput – The overall throughput or bandwidth of a RAID 0 array can equal the sum of each disk’s bandwidth since data transfers occur in parallel.
- Full capacity utilization – RAID 0 makes use of the full capacity of all disks with no overhead for parity or redundancy. The total array capacity equals the sum of all disk capacities.
- Cost effective – RAID 0 is inexpensive to implement as it uses the bare minimum number of disks with no need for parity or spare disks.
For scenarios where absolute performance is critical and fault tolerance is less important, RAID 0 provides fast performance at a low cost. The key tradeoff is increased risk of data loss if a drive fails.
Disadvantages of Disk Striping
While disk striping improves performance, there are some downsides to consider:
- No fault tolerance – Since data is spread across all disks with no parity or duplication, the failure of just one disk will result in full data loss for the array. RAID 0 has no redundancy.
- Reduced reliability – The lack of redundancy means the reliability of a RAID 0 array is less than that of a single disk. The probability of array failure is equal to the sum of failure probabilities of each disk.
- Replication required – To protect against data loss, RAID 0 arrays require replication and regular backups. Additional redundancy solutions are mandatory.
- Partial disk failure – If sectors on a disk become corrupted or unreadable, all striped data across the array could be compromised or lost entirely.
While the performance gains can be substantial, RAID 0 is best suited to non-critical data where backups are available. The increased risk of catastrophe makes RAID 0 inappropriate for mission critical or highly availability systems.
RAID 0 Configurations
RAID 0 arrays can be configured with different numbers of disks, block sizes, and stripe sizes to optimize for bandwidth or I/O operations per second (IOPS):
- Disks – Using more disks increases overall array bandwidth. Typical RAID 0 setups use between 2 to 8 disks.
- Block size – Smaller blocks mean finer data granularity but more processing overhead. Typical block sizes range from 4KB to 128KB.
- Stripe size – Determines how data is apportioned between disks. Larger stripes increase sequential throughput while smaller stripes improve IOPS.
Each parameter impacts performance and should be tested with the expected workloads. In general, more disks with larger stripes and medium block sizes provide the highest overall bandwidth. Smaller stripes and blocks improve random I/O performance.
RAID 0 vs Other RAID Levels
Compared to other standard RAID levels, RAID 0 differs in the areas of performance, fault tolerance, and implementation cost:
|RAID Type||Fault Tolerance||Read Performance||Write Performance||HDDs Required||Cost|
RAID 0 provides the fastest read and write performance but no fault tolerance. RAID 1 and 6 offer good redundancy but slower writes. RAID 5 offers a balance with decent performance and redundancy.
Ideal Uses for RAID 0
Due to its characteristics, RAID 0 works well in these scenarios:
- Gaming PCs – Gamers desire fast load times and level transitions, making RAID 0 a good choice.
- Workstations – For intensive workstation tasks like video production, RAID 0 provides performance gains.
- Scientific computing – Big data analysis and scientific simulations benefit from the parallelism of RAID 0.
- Database indexing – Indexes can be striped for faster seeks and reduced query times.
- Scratch data – Temporary caches and buffers require fast IO and minimal redundancy.
- Transaction logs – Logging performance improves with RAID 0’s fast sequential writes.
Any application where maximum speed is vital and backups are available is a good candidate for RAID 0 storage.
Drawbacks of Using RAID 0
RAID 0 has some notable drawbacks that limit its uses for mission critical data:
- No redundancy means any disk failure leads to total data loss.
- RAID 0 cannot tolerate a single faulty sector or unreadable block.
- Rebuild times are extremely slow compared to fault tolerant RAID levels.
- There is no background data integrity checking like in RAID 5 or 6.
- Partial disk failures can quickly cascade into array-wide corruptions.
- Heavy write workloads can wear out disks faster than in mirrored RAID.
- RAID 0 is risky for applications that demand high availability or uptime.
Due to the lack of redundancy, RAID 0 is generally unsuitable for storing critical data, databases, financial records, or any data that would be difficult to reconstruct after a disk failure.
Performance Optimization Tips
To maximize performance in a RAID 0 array, consider these tips:
- Use the fastest disk drives possible such as SSDs or high RPM HDDs.
- Add additional disks to increase overall array bandwidth.
- Test different block and stripe sizes for your specific workloads.
- Align partitions and stripes for optimal performance.
- Place swap files and temporary data on the array.
- Isolate the RAID 0 disks from parity-based RAID traffic.
- Use modern SATA/SAS controllers and the latest firmware.
Benchmark tools can dial in block and stripe sizes. Enterprise class SSDs, disk controllers, and avoiding disk bottlenecks are key for top speed.
Implementation Best Practices
To successfully deploy RAID 0, follow these best practices:
- Use same size, speed and type of disks.
- Configure RAID card settings for optimal performance.
- Align partitions and stripes to cylinder boundaries.
- Use moderately sized stripes between 64KB to 256KB.
- Monitor disk health and temperatures closely.
- Implement regular and frequent backups.
- Scrub drives periodically to correct soft errors.
- Hot spare disks can automatically rebuild RAID 1 mirrors.
Careful configuration, health monitoring, and backups are necessary to achieve high performance while minimizing downtime and data loss.
Alternatives to RAID 0
Some alternatives to RAID 0 provide redundancy and fault tolerance:
- RAID 1 (Mirroring) – Disk mirroring provides redundancy but at doubled hardware cost.
- RAID 5 (Striping with Distributed Parity) – Parity allows one disk failure to be tolerated with minimal performance impact.
- RAID 10 (Stripped Mirrors) – Combines mirroring and striping for fault tolerance and speed.
- RAID 50/60 (Nested Striping) – Large arrays can stripe RAID 5 groups for expanded capacity and performance.
For mission critical data, redundant RAID levels like 10 or 50 may offer a suitable balance of speed and reliability compared to fragile RAID 0.
Software vs Hardware RAID
RAID 0 can be implemented in software or hardware:
- Software RAID
- Managed by operating system using CPU
- More flexibility in configuration
- Lower cost, uses existing disks and processors
- Hardware RAID
- Dedicated RAID controller required
- Higher performance, handles RAID processing
- More reliable, keeps operating if OS crashes
- Typically supports advanced feature sets
- More expensive due to added hardware
Software RAID is a good choice for home builds on a budget. Hardware RAID performs better under heavy workloads and offers redundancy if the OS goes offline.
Disk striping in RAID 0 can provide substantial performance benefits through parallelism. However, the lack of fault tolerance means RAID 0 is best limited to non-critical data where backups are regularly performed. For mission critical data, redundant RAID levels are a safer choice despite their capacity and write speed penalties. With proper health monitoring and maintenance, RAID 0 can deliver excellent speed for applications where uptime is less important than all-out performance.