We have all heard for years about tiered data storage for disk arrays. Tier 1 is usually enterprise disk, which was once
Fibre Channel but more and more is becoming
SAS. Tier 2 is typically enterprise
SATA, while tier 3 might be consumer-grade drives. And the last year or two has seen the rise of a tier 0 for flash-based solid state drives (
SSDs).
There are big differences between each of the tiers in terms of reliability, performance, data integrity and cost, especially for tier 0 SSDs. Here is a quick review of some of the major differences between the disk tiers:
| Drive type and interface |
Tier 1 FC and SAS |
Tier 2 SATA |
Tier 3 SATA |
| Performance |
Best transfer rates and best seek and latency time |
2x seek and latency time; 25% less performance |
Seek time is the same as tier 2, but lower performance |
| Size |
3.5 inch; moving to 2.5 |
3.5 inch |
3.5 inch |
| Annualized Failure Rate |
Best |
Second best |
Worst |
| Bit Error Rate |
1 sector in 10E16 bits |
1 sector in 10E15 bits |
1 sector in 10E14 bits |
| Cost |
Highest cost; usually about 8x per GB over tier 3 |
High cost; usually about 2x per GB tier 3 |
Lowest cost |
|
This table does not include SSDs, of course, which have a wide range of reliability and performance and might need their own tiers.
Read the rest at Enterprise Storage Forum.