Re: SCSI tape access on 2.6 kernels?

Kai Makisara
2006-01-25T21:08:46Z

On Tue, 24 Jan 2006, Chip Coldwell wrote:

> On Tue, 24 Jan 2006, Patrick Mansfield wrote:
>
> > On Tue, Jan 24, 2006 at 12:52:36PM -0500, Chip Coldwell wrote:
> >
> > > Put
> > >
> > > options st try_direct_io=0
> >
> > >
> > > in /etc/modprobe.conf. Direct I/O defeats read-ahead, and
> > > significantly (factor of >5) degrates read performance. I don't know
> > > about writes.
> >
> > For tape???
>
> Yes, for tape. We verified this with a DAT72 DDS drive.
>
How did you do the tests? I would like to be able to reproduce this
finding because there is something wrong somewhere. With any decent read()
and write() byte counts (the 64 kB you mention in another message is
decent) you should not find direct i/o slower than using the driver
buffer. I have not seen anything like this with my DDS-4 drive (same
speed as DAT72).

--
Kai