Date: Thu, 28 Apr 2005 15:57:28 +0100 From: "Steven Hartland" <killing@multiplay.co.uk> To: "Eric Anderson" <anderson@centtech.com> Cc: freebsd-performance@freebsd.org Subject: Re: Very low disk performance Highpoint 1820a Message-ID: <06d301c54c02$98ab5ce0$7f06000a@int.mediasurface.com> References: <069901c54bfd$2967ba40$7f06000a@int.mediasurface.com> <4270F648.5030501@centtech.com>
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----- Original Message -----
From: "Eric Anderson" <anderson@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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