Re: Serial Console and Slow SCSI Disk Access?

Helge Hafting
2006-06-19T06:53:47Z

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