Very low disk performance Highpoint 1820a

[Steven Hartland]

----- Original Message ----- 
From: "Eric Anderson" <anderson at centtech.com>

>> Where do I start looking?

> First, understand that RAID 5 is dependant on fast hardware to performa 
> the XOR operations.  A single disk without any RAID can easily 
> outperform a RAID array if the RAID array is on a 'slow' controller. 
> The Highpoint controllers are not exactly high-end fast RAID 
> controllers, so ~50MB/s isn't too bad for that I would say.  Did you 
> happen to try a vinum RAID5?  How about a stripe?

The quoted benchmarks for this controller are ~500MB/s with 8 
raptor disks. Its a hardware RAID 5 with 8 SATA channels on 64Bit PCI-X
@ 133Mhz so under the current setup it should be achieving ~250MB/s
Im only getting 50MB/s which is just silly.

It was also my inderstanding that the XOR is only done on write
not read.

> You could make two RAID 5's with the controller, and then stripe those 
> in vinum.  You could also do a combo of two stripes in the controller, 
> and a vinum mirror in FreeBSD - that would give you decent performance.

I could but it seems there is something more problematic a foot
here and would like to investigate the reason for the poor performance
not workaround it.

    Steve


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