Re: Serial Console and Slow SCSI Disk Access?

[Helge Hafting]

Jeff Gold wrote:
> Mark Lord wrote:
> > This can happen if there are kernel messages being printed on the 
> > serial console.
> > If all is quiet, I would expect things to be as fast as normal 
> > elsewhere.
>
> Thank you for the suggestion.  I don't see much in /var/log/messages 
> (syslogd is running).  There are 3326 lines taking up about 256 kB 
> there, and when I run hdparm runs no further messages are generated.
>
> I don't have anything attached to the serial port at the moment.  
> Could that cause problems?  I'm going to attach something and see what 
> happens.  Other advice is still welcome. 
With nothing attached, any write to the serial device might go through
a lengthy timeout because of flow control.  I'd consider that a bug
in this case though, and there is usually no console printout
per scsi disk access either.


I would not be surprised if your serial console causes a longer boot time,
as all boot messages have to be transferred over the slow serial link
or in the worst case timed out one message at a time.

But I can't see why it'd make scsi disks slower. The scsi host adapter 
initialization
writes some messages of course, but there should be no more console accesses
during a hdparm test run.

Helge Hafting
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