FreeBSD 5.3b7and poor ata performance

[fandino]

Hello Søren,

Søren Schmidt wrote:
>>> GNU/Linux 2.4.18 with ext2:               56848 K/sec
>>> FreeBSD 5.3b7 with default fs:            26347 K/sec
>>> FreeBSD 5.3b7 with default fs(async):     26566 K/sec
>>> FreeBSD 5.3b7 ata raid0* (two disks):     26131 K/sec
>>> FreeBSD 5.3b7 geom stripe* (two disks):   30063 K/sec
>>> FreeBSD 5.3b7 geom stripe** (four disks): 31891 K/sec
>>> OpenBSD 3.5 UFS fs:                       55277 K/sec
>>>
>>> * Each disk of the raid had a throughput of approx. 15000 K/sec
>>> ** Each disk of the raid had a throughput of approx. 7500 K/sec
>>> Each disk of the read split the throughput by half.
>>>
>>> How is possible that FreeBSD performs as bad?
>>>
>>>
>> If you're still using the GENERIC kernel, that could explain it, and 
>> judging
>> from other emails I've seen from you, you're still using the GENERIC 
>> kernel.
> 
> Right, and you should also use -U (softupdates) on you newfs line.



FreeBSD 5.3b7 with default fs(+softupdates):   26615 K/sec
http://195.55.55.164/tests/fbsd+softupdates.txt



I was running FreeBSD-4.x for two years with this problem, waiting
for FreeBSD-5 because ATAng looks very promising.

Unfortunately the performance problem persist :-( and I'd like to
call the attention about performance over raw devices, whilst it's
a very scientific test it's very curious:

# dd if=/dev/ad4 of=/dev/null bs=1024k count=1024
1024+0 records in
1024+0 records out
1073741824 bytes transferred in 31.090536 secs (34535970 bytes/sec)

over 34000 K/sec, using raw devices (for sequential access obviously)
not softupdates, filesystems or caches are involved, and with all this
FreeBSD performace is very deficient. Tests with OpenBSD and Linux
using raw devices shows a throughput of approx 60000 K/sec.
The question here is why using low-level access to disks is so bad?

Perphas I'm missing something but this seems very weird to me.

I'd like to know wich is you opinion about this.

Thank you.