Slow PCI-X controller perfomance (adaptec 2130SLP)

[Björn König]

Vasim Valejev wrote:

> I've tried to set up FreeBSD-current on Dual opteron box with Adaptec 2130SLP
> PCI-X RAID controller (256MB memory). My tests did show that maximum transfer
> rate from controller to OS was about 132MB/s. That is very strange since PCI-X
> maximum speed should be about 1GB/s. Why the controller was so slow? [...]

132 MB/s is a very good transfer rate. Keep in mind that 1 GB/s is the 
theoretical limit of the PCI-X bus which means that single devices do 
not necessarily accomplish this transfer rate. As far as I can remember 
the maximum read transfer rate of a RAID 5 is n - 1, i.e. if one drive 
has a maximum transfer rate of 80 MB/s then three of them in a RAID 5 
array can't have more than 160 MB/s.

Björn