Recently, in the global computer press has begun to appear quite a few articles on the topic "Why RAID-5 is bad” (here are some examples: one, two, and others).
We will try to explain why RAID-5 has worked so far, but now it suddenly stopped.
The capacity of hard drives has been growing without any specific tendency to a stoppage over the past few years. In addition, the capacity of the drives almost doubles every year, but their data transfer rate does not increase much over the same period. Yes, indeed, the drives get interfaces, such as SATA and SATA-II, and SATA-III is on its way, but there is a question “would these drives work faster?” or they just get new interfaces with the numbers of theoretical characteristics.
The usage of hard drives tells us that the capacity grows and the speed does not.
Improving performance of the disk subsystem is the most topical issue today. This is caused by the low cost of HDD that takes a leading position in the mass segment. More than a half of the resource-intensive applications have a "vulnerable spot" that are the spindle drives. In this case, everything does not depend on the bandwidth of SATA interface, but it depends on the physical capabilities of the mechanical components of the magnetic disk. The bandwidth of SATA-II and SATA-III interfaces makes 300MB/s and 600MB/s respectively, and the maximum performance that can provide a regular HDD does not exceed 150MB/s. Therefore, the transition to SATA-III-interface will be reasonable only for SSD, but it is not suitable for everyone.
In order to evaluate and to test the effectiveness of different types of disk subsystems were chosen following solutions:
1. OCZ RevoDrive X2 PCI-E SSD 100Gb
2. Plextor PX-128M2S SSD 128Gb