Very low disk performance Highpoint 1820a

[Willem Jan Withagen]

Steven Hartland wrote:
>> Still I would argue that if you do not use a write size larger than 
>> what you have as real memory, that buffering in real memory is going 
>> to play a role....
> 
> 
> I think you miss read all the details here Willem.

Sorry about that, if that is the case.

> Original values:
> Write: 150Mb/s
> Read: 50Mb/s
> Current value after tweeking, RAID stripe size, vfs.read_max and
> MAXPHYS ( needs more testing now due to scotts warning )
> Write: 150Mb/s
> Read: 200Mb/s
> 
> Note: The test size was upped to 10Gb to avoid caching issues.

That would certainly negate my assumption 10G is enough to regularly flush the 
buffer.

>> Other than that I find 50Mb/s is IMHO reasonable high value for a 
>> RAID5 in writting. But it would require substantial more organised 
>> testing. DD is nothing more than a very crude indication of what to 
>> expect in real life.
> 
> 
> dd was uses as it is a good quick indication of baseline sequential file 
> access
> speed and as such highlighted a serious issue with the original 
> performance.

That is well phrased English for what I was trying to say. I'm glad to see 
that it worked for you. And I'm certainly impressed by the numbers...

This is on a 4 disk RAID5 with one hot spare???

--WjW