Filter
Top Products
1.6.6.8 Summary of RAID Performance Characteristics
RAID-0:
Block Interleave Data Striping without parity
•
Fastest data-rate performance
•
Allows seek and drive latency to be performed in parallel
•
Significantly outperforms single large disk
RAID-1:
Disk Mirroring/Disk Duplexing and Data Strip mirroring (RAID-1,
Enhanced)
•
Fast and reliable, but requires 100% disk space overhead
•
Data copied to each set of drives
•
No performance degradation with a single disk failure
•
RAID-1 enhanced provides mirroring with an odd number of drives
RAID-2:
Bit Interleave Data Striping with Hamming Code
•
Very fast for sequential applications, such as graphics modelling
•
Almost never used with PC-based systems
RAID-3:
Bit Interleave Data Striping with Parity
•
Access to all drives to retrieve one record
•
Best for large sequential reads
•
Very poor for random transactions
•
Poor for any write operations
•
Faster than a single drive, but much slower than RAID-0 or RAID-1 in random
environments
RAID-4:
Block Interleave Data Striping with one Parity Disk
•
Best for large sequential I/O
•
Very poor write performance
•
Faster than a single drive, but usually much slower than RAID-0 or RAID-1
RAID-5:
Block Interleave Data Striping with Skewed Parity
•
Best for random transactions
•
Poor for large sequential reads if request is larger than block size
•
Better write performance than RAID-3 and RAID-4
•
Block size is key to performance, must be larger than typical request size
•
Performance degrades in recovery mode (when a single drive has failed)
Table 7. Summary of RAID Performance Characteristics
RAID Level Capacity Large Transfers High I/O Rate Data Availability
Single Disk Fixed (100%) Good Good 1
RAID-0 Excellent Very Good Very Good Poor 2
RAID-1 Moderate (50%) Good Good Good
RAID-2 Very Good Good Poor Good
RAID-3 Very Good Very Good Poor Good
RAID-4 Very Good Very Good Poor Good
RAID-5 Very Good Very Good Good Good
Note:
1The MTBF (mean time before failure) for single disks can range from 10,000 to 1,000,000 hours.
2Availability = MTBF of one disk divided by the number of disks in the array.
30 NetWare Integration Guide