Recommened U320 SCSI controller (pci-x)?

[Bernard Buri]

Nico -telmich- Schottelius wrote:
> Bernard Buri [Wed, Jun 06, 2007 at 10:24:05PM +0200]:
>> Hi!
>>
>> Not only for FreeBSD, I have the best experience with the mpt fusion 
>> based cards, concerning performance and compatibility/reliability. 
> 
> Do you have some card names? Searching for the 53c010 on the lsi logic
> page was quite confusing, because it seems to link to other cards that
> use the amr driver, which is another chip, afaiu.
> 
>> Currently, we have a subversion server running FreeBSD 6.2 without any 
>> problems on an mpt based raid controller. I believe it is U160 though.
> 
> Ok. We are trying to run a high-load mailserver over here and thus the
> disk i/o is a big issue (and locking up the server a big problem).
> 
> Nico
> 
We have a "Feiertag==no one is in office" today, and there was a 
technical problem yesterday evening. Some servers are down obviously so 
I cannot lookup which product is built in exactly. I can find out 
tomorrow though.

Are you looking for hardware raid, or do you want to do software raid ?

Another question that comes to my mind:

Did you analyze the disk i/o any further ?
My experience with FreeBSD shows, that upgrading the main memory 
generously (2 or 4 GB) will allow the system to fill the buffer cache 
with file data, while leaving the "Namei lookup cache" constrained to 
some degree.

If you run systat -vmstat 1, you can see everything on one place:

1.) On the bottom, you can see the actual disk utilization.
2.) Above, you can watch the "Namei" cache behaviour.
3.) On top, you see Free Memory, that is: memory that is not used at all

So, on my Mac mini which has a very slow disk I face the following 
situation: I run du -h -d1 /usr/ports to fill the Namei cache. Now I 
watch the statistics in systat and run du again:
1.) I see actual disk i/o happening on my drive
2.) I see Namei cache hits dropping to ~45%
3.) I see about 300MB of memory unused.

Most of the mailserver softwares are using many small files, and I guess 
that the lookup cache should improve the overall performance more than a 
fast drive. If you see low Namei hit rates, perhaps there is information 
available on how to tune the cache ?