Very low disk performance Highpoint 1820a

[Eric Anderson]

Steven Hartland wrote:
> ----- 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.

Correct - I misread the dd line.  When you are doing the dd, what is 
your system busy doing?   (top/ps info)


>> 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.

What do you suspect?

Some info from one of my arrays:

# dd if=/dev/zero of=./testfile bs=64k count=10000
10000+0 records in
10000+0 records out
655360000 bytes transferred in 3.581413 secs (182989226 bytes/sec)

(unmount / mount filesystem)
# dd if=./testfile of=/dev/null bs=64k count=10000
10000+0 records in
10000+0 records out
655360000 bytes transferred in 6.747707 secs (97123362 bytes/sec)

# dd if=/dev/da0s1d of=/dev/null bs=64k count=10000
10000+0 records in
10000+0 records out
655360000 bytes transferred in 11.252226 secs (58242699 bytes/sec)

Seems like the reads should be faster than the writes..

Eric



-- 
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Eric Anderson        Sr. Systems Administrator        Centaur Technology
A lost ounce of gold may be found, a lost moment of time never.
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