On Mon, Apr 11, 2011 at 19:09:00 +0300, Alexander Motin wrote:
> On 11.04.2011 18:43, Kenneth D. Merry wrote:
> >On Sun, Apr 10, 2011 at 23:19:31 +0300, Alexander Motin wrote:
> >>Alexander Best wrote:
> >>>2) the pass* devices still don't show up under ide/scsi/other. that's 
> >>>ok, but
> >>>    then the src comments and manual pages need to be changed 
> >>>    accordingly.
> >>
> >>As I have told - it is a bug/feature of libdevstat. It should not be
> >>difficult to fix, if it is really a bug.
> >
> >That was intentional, if I can remember what I intended in 1997/1998.
> >
> >The reason was that since there is one passthrough device created for every
> >device that CAM manages, you don't want to show pass(4) devices when the
> >user says 'iostat -t scsi'.  Otherwise he might get all pass(4) devices,
> >depending on the order of devices in the system.
> >
> >But, if it's pass(4) devices you want, you can ask for them specifically,
> >or for all SCSI/IDE pass(4) devices, as mav did above.
> But it is impossible to get, for example, all SCSI devices including 
> pass. Either only non-pass, or pass only.
> It is strange that if I won't specify "-t" (most probable for 
> inexperienced users), I'll gel all devices including pass, but if 
> specify "-t scsi" (as more advanced user who knows what to ask), I'll 
> get only non-pass. It is at least inconsistent.

Perhaps it is somewhat inconsistent, and we should do some filtering by
default to not show pass(4) devices.

The idea was that in most cases, people will not want to see the pass(4)
devices.  That is not where most of the I/O typically happens.  If they
want to see the pass(4) devices, they can ask for them specifically by type
or by name.

When I have a system full of drives and I want to look at one particular
pass(4) device, I always specify it manually, e.g.:  'iostat -d pass4 1'

Kenneth Merry
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