[linux-lvm] lv not persistent across reboot?

[linux-lvm] lv not persistent across reboot?

[Tim Pepper]

I've set up a little test machine to play with lvm.  It's running RedHat 6.2
with a 2.4-test8 kernel and lvm 0.8.

I've successfully created and used an lv (with a reiserfs filesystem on top
of it).  My problem is that when I reboot the lv is gone.  vgscan finds
nothing.  pvdisplay, lvdisplay and vgdisplay likewise show nothing.  If I go
through the steps though to recreate the lvm, pvcreate seems to think
something's there and wants me to do a '-ff'.  I can then continue on.

Playing around I see:

	[root@qalab5 /root]# umount /mnt/nz
	
	[root@qalab5 /root]# lvdisplay /dev/netzero/big 
	--- Logical volume ---
	LV Name               /dev/netzero/big
	VG Name               netzero
	LV Write Access       read/write
	LV Status             available
	LV #                  1
	# open                0
	LV Size               34.18 GB
	Current LE            8750
	Allocated LE          8750
	Allocation            next free
	Read ahead sectors    120
	Block device          58:0
	
	[root@qalab5 /root]# vgscan
	vgscan -- reading all physical volumes (this may take a while...)
	vgscan -- no volume groups found

	[root@qalab5 /root]# lvdisplay /dev/netzero/big 
	lvdisplay -- ERROR: VGDA in kernel and lvmtab are NOT consistent; please run
	vgscan

	[root@qalab5 /root]# vgscan
	vgscan -- reading all physical volumes (this may take a while...)
	vgscan -- no volume groups found
	
	[root@qalab5 /root]# mount /mnt/nz

I can't seem to display it, but it does remount here.

I was thinking that maybe the 'vgchange -a n' shouldn't be done or perhaps I
was doing it at the wrong time (at shutdown after the filesystem on the lv was
umounted), but the above seems flakey even without vgchange in the picture.

Any ideas what could be going on?  Thanks in advance for any help.

Tim

--
*********************************************************
*  tim.pepper@opensales dot com     * Venimus, Vidimus, *
*  http://www.opensales.com         * Dolavimus         *
*********************************************************

Re: [linux-lvm] lv not persistent across reboot?

[Jan Niehusmann]

On Tue, Sep 26, 2000 at 11:35:21AM +0000, Heinz J. Mauelshagen wrote:
> Just recently i faced the efect with 2.4.0-test8, that devices where
> exposed multiple times. For eg. /dev/sdb and /dev/sdf accessed the same drive.

It's easily fixed if you comment out the last two lines of drivers/block/sd.c,
or correctly fixed in later test9-preX-Kernels. 
(if you comment out the lines in sd.c, please remember to uncomment them if
you patch your kernel up to a newer version)

Jan

Re: [linux-lvm] lv not persistent across reboot?

[Heinz J. Mauelshagen]

Just recently i faced the efect with 2.4.0-test8, that devices where
exposed multiple times. For eg. /dev/sdb and /dev/sdf accessed the same drive.

Sent a message to linux-kernel.

Here's a temporary workaround for the LVM 0.8final library to deal
with this bug.


Please replace the loop block in tools/lib/pv_read_all_pv_of_vg.c
starting at line 84 by:

      for ( p = 0; pv_tmp != NULL && pv_tmp[p] != NULL; p++) {
         if ( pv_check_consistency ( pv_tmp[p]) < 0) continue;

         /* avoid dual access pathes for now (2.4.0-test8) */
         for ( i = 0; i < np; i++) {
            if ( pv_tmp[i] == NULL) continue;
            if ( strncmp ( pv_tmp[i]->vg_name, pv_tmp[p]->vg_name,
                           NAME_LEN) == 0 &&
                 pv_tmp[i]->pv_number == pv_tmp[p]->pv_number &&
                 strncmp ( pv_tmp[i]->pv_uuid, pv_tmp[p]->pv_uuid,
                           UUID_LEN) == 0) {
               free ( pv_tmp[p]);
               pv_tmp[p] = NULL;
               goto pass_end;
            }
         }

         if ( strcmp ( pv_tmp[p]->vg_name, vg_name) == 0) {
            if ( pv_number < pv_tmp[p]->pv_number)
               pv_number = pv_tmp[p]->pv_number;
            np++;
         }
pass_end:
      }


Gimme feedback if it works for you.

Regards,
Heinz      -- The LVM guy --

On Mon, Sep 25, 2000 at 04:52:40PM -0700, Tim Pepper wrote:
> I've set up a little test machine to play with lvm.  It's running RedHat 6.2
> with a 2.4-test8 kernel and lvm 0.8.
> 
> I've successfully created and used an lv (with a reiserfs filesystem on top
> of it).  My problem is that when I reboot the lv is gone.  vgscan finds
> nothing.  pvdisplay, lvdisplay and vgdisplay likewise show nothing.  If I go
> through the steps though to recreate the lvm, pvcreate seems to think
> something's there and wants me to do a '-ff'.  I can then continue on.
> 
> Playing around I see:
> 
> 	[root@qalab5 /root]# umount /mnt/nz
> 	
> 	[root@qalab5 /root]# lvdisplay /dev/netzero/big 
> 	--- Logical volume ---
> 	LV Name               /dev/netzero/big
> 	VG Name               netzero
> 	LV Write Access       read/write
> 	LV Status             available
> 	LV #                  1
> 	# open                0
> 	LV Size               34.18 GB
> 	Current LE            8750
> 	Allocated LE          8750
> 	Allocation            next free
> 	Read ahead sectors    120
> 	Block device          58:0
> 	
> 	[root@qalab5 /root]# vgscan
> 	vgscan -- reading all physical volumes (this may take a while...)
> 	vgscan -- no volume groups found
> 
> 	[root@qalab5 /root]# lvdisplay /dev/netzero/big 
> 	lvdisplay -- ERROR: VGDA in kernel and lvmtab are NOT consistent; please run
> 	vgscan
> 
> 	[root@qalab5 /root]# vgscan
> 	vgscan -- reading all physical volumes (this may take a while...)
> 	vgscan -- no volume groups found
> 	
> 	[root@qalab5 /root]# mount /mnt/nz
> 
> I can't seem to display it, but it does remount here.
> 
> I was thinking that maybe the 'vgchange -a n' shouldn't be done or perhaps I
> was doing it at the wrong time (at shutdown after the filesystem on the lv was
> umounted), but the above seems flakey even without vgchange in the picture.
> 
> Any ideas what could be going on?  Thanks in advance for any help.
> 
> Tim
> 
> --
> *********************************************************
> *  tim.pepper@opensales dot com     * Venimus, Vidimus, *
> *  http://www.opensales.com         * Dolavimus         *
> *********************************************************

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

Heinz Mauelshagen                                 Sistina Software Inc.
Senior Consultant/Developer                       Bartningstr. 12
                                                  64289 Darmstadt
                                                  Germany
Mauelshagen@Sistina.com                           +49 6151 7103 86
                                                       FAX 7103 96
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

Re: [linux-lvm] lv not persistent across reboot?

[Tim Pepper]

On Tue, 26 Sep 2000, Jan Niehusmann wrote:

> It's easily fixed if you comment out the last two lines of drivers/block/sd.c,
> or correctly fixed in later test9-preX-Kernels. 

Is that drivers/scsi/sd.c or did it get moved between test8 and test9-preX?

--
*********************************************************
*  tim.pepper@opensales dot com     * Venimus, Vidimus, *
*  http://www.opensales.com         * Dolavimus         *
*********************************************************

Re: [linux-lvm] lv not persistent across reboot?

[Jan Niehusmann]

On Tue, Sep 26, 2000 at 07:44:40AM -0700, Tim Pepper wrote:
> On Tue, 26 Sep 2000, Jan Niehusmann wrote:
> 
> > It's easily fixed if you comment out the last two lines of drivers/block/sd.c,
> > or correctly fixed in later test9-preX-Kernels. 
> 
> Is that drivers/scsi/sd.c or did it get moved between test8 and test9-preX?

Of course drivers/scsi/sd.c, I'v been confused by the lvm.c move in test9-preX
:-)

Jan

Re: [linux-lvm] lv not persistent across reboot?

[Tim Pepper]

On Tue, 26 Sep 2000, Jan Niehusmann wrote:

> It's easily fixed if you comment out the last two lines of drivers/block/sd.c,
> or correctly fixed in later test9-preX-Kernels. 

This appears to have indeed fixed the problem.  Many thanks for your help!

Tim

--
*********************************************************
*  tim.pepper@opensales dot com     * Venimus, Vidimus, *
*  http://www.opensales.com         * Dolavimus         *
*********************************************************

Re: [linux-lvm] lv not persistent across reboot?

[Steve Brueggeman]

Does this imply that Linux LVM will also have problems with discs in H.A.
configurations? 

For example: Fibre Channel drives have two ports on them.  If I have a Linux box
with two Host Adapters, and each adapter is connected to the same set of drives,
but on different ports, will v0.8final (without the patch below) have unstable
vgscans?

I have not been following the high availability mailing list, and a solution may
already exist  there.  If so, and you know how, I'd be interested in a quick
description.

Later,

Steve Brueggeman

On Tue, 26 Sep 2000 11:35:21 +0000, you wrote:

>
>Just recently i faced the efect with 2.4.0-test8, that devices where
>exposed multiple times. For eg. /dev/sdb and /dev/sdf accessed the same drive.
>
>Sent a message to linux-kernel.
>
>Here's a temporary workaround for the LVM 0.8final library to deal
>with this bug.
>
>
>Please replace the loop block in tools/lib/pv_read_all_pv_of_vg.c
>starting at line 84 by:
>
>      for ( p = 0; pv_tmp != NULL && pv_tmp[p] != NULL; p++) {
>         if ( pv_check_consistency ( pv_tmp[p]) < 0) continue;
>
>         /* avoid dual access pathes for now (2.4.0-test8) */
>         for ( i = 0; i < np; i++) {
>            if ( pv_tmp[i] == NULL) continue;
>            if ( strncmp ( pv_tmp[i]->vg_name, pv_tmp[p]->vg_name,
>                           NAME_LEN) == 0 &&
>                 pv_tmp[i]->pv_number == pv_tmp[p]->pv_number &&
>                 strncmp ( pv_tmp[i]->pv_uuid, pv_tmp[p]->pv_uuid,
>                           UUID_LEN) == 0) {
>               free ( pv_tmp[p]);
>               pv_tmp[p] = NULL;
>               goto pass_end;
>            }
>         }
>
>         if ( strcmp ( pv_tmp[p]->vg_name, vg_name) == 0) {
>            if ( pv_number < pv_tmp[p]->pv_number)
>               pv_number = pv_tmp[p]->pv_number;
>            np++;
>         }
>pass_end:
>      }
>
>
>Gimme feedback if it works for you.
>
>Regards,
>Heinz      -- The LVM guy --
>
>On Mon, Sep 25, 2000 at 04:52:40PM -0700, Tim Pepper wrote:
>> I've set up a little test machine to play with lvm.  It's running RedHat 6.2
>> with a 2.4-test8 kernel and lvm 0.8.
>> 
>> I've successfully created and used an lv (with a reiserfs filesystem on top
>> of it).  My problem is that when I reboot the lv is gone.  vgscan finds
>> nothing.  pvdisplay, lvdisplay and vgdisplay likewise show nothing.  If I go
>> through the steps though to recreate the lvm, pvcreate seems to think
>> something's there and wants me to do a '-ff'.  I can then continue on.
>> 
>> Playing around I see:
>> 
>> 	[root@qalab5 /root]# umount /mnt/nz
>> 	
>> 	[root@qalab5 /root]# lvdisplay /dev/netzero/big 
>> 	--- Logical volume ---
>> 	LV Name               /dev/netzero/big
>> 	VG Name               netzero
>> 	LV Write Access       read/write
>> 	LV Status             available
>> 	LV #                  1
>> 	# open                0
>> 	LV Size               34.18 GB
>> 	Current LE            8750
>> 	Allocated LE          8750
>> 	Allocation            next free
>> 	Read ahead sectors    120
>> 	Block device          58:0
>> 	
>> 	[root@qalab5 /root]# vgscan
>> 	vgscan -- reading all physical volumes (this may take a while...)
>> 	vgscan -- no volume groups found
>> 
>> 	[root@qalab5 /root]# lvdisplay /dev/netzero/big 
>> 	lvdisplay -- ERROR: VGDA in kernel and lvmtab are NOT consistent; please run
>> 	vgscan
>> 
>> 	[root@qalab5 /root]# vgscan
>> 	vgscan -- reading all physical volumes (this may take a while...)
>> 	vgscan -- no volume groups found
>> 	
>> 	[root@qalab5 /root]# mount /mnt/nz
>> 
>> I can't seem to display it, but it does remount here.
>> 
>> I was thinking that maybe the 'vgchange -a n' shouldn't be done or perhaps I
>> was doing it at the wrong time (at shutdown after the filesystem on the lv was
>> umounted), but the above seems flakey even without vgchange in the picture.
>> 
>> Any ideas what could be going on?  Thanks in advance for any help.
>> 
>> Tim
>> 
>> --
>> *********************************************************
>> *  tim.pepper@opensales dot com     * Venimus, Vidimus, *
>> *  http://www.opensales.com         * Dolavimus         *
>> *********************************************************
>
>=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
>
>Heinz Mauelshagen                                 Sistina Software Inc.
>Senior Consultant/Developer                       Bartningstr. 12
>                                                  64289 Darmstadt
>                                                  Germany
>Mauelshagen@Sistina.com                           +49 6151 7103 86
>                                                       FAX 7103 96
>=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-


_________________________________________________________
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Re: [linux-lvm] lv not persistent across reboot?

[Heinz J. Mauelshagen]

Morning Steve :-{)

On Wed, Sep 27, 2000 at 07:19:14AM -0500, Steve Brueggeman wrote:
> Does this imply that Linux LVM will also have problems with discs in H.A.
> configurations? 

Yes.

> 
> For example: Fibre Channel drives have two ports on them.  If I have a Linux box
> with two Host Adapters, and each adapter is connected to the same set of drives,
> but on different ports, will v0.8final (without the patch below) have unstable
> vgscans?

Yes, it should.

> 
> I have not been following the high availability mailing list, and a solution may
> already exist  there.  If so, and you know how, I'd be interested in a quick
> description.

Not that i am aware of.

Cheers,
Heinz

> 
> Later,
> 
> Steve Brueggeman
> 
> On Tue, 26 Sep 2000 11:35:21 +0000, you wrote:
> 
> >
> >Just recently i faced the efect with 2.4.0-test8, that devices where
> >exposed multiple times. For eg. /dev/sdb and /dev/sdf accessed the same drive.
> >
> >Sent a message to linux-kernel.
> >
> >Here's a temporary workaround for the LVM 0.8final library to deal
> >with this bug.
> >
> >
> >Please replace the loop block in tools/lib/pv_read_all_pv_of_vg.c
> >starting at line 84 by:
> >
> >      for ( p = 0; pv_tmp != NULL && pv_tmp[p] != NULL; p++) {
> >         if ( pv_check_consistency ( pv_tmp[p]) < 0) continue;
> >
> >         /* avoid dual access pathes for now (2.4.0-test8) */
> >         for ( i = 0; i < np; i++) {
> >            if ( pv_tmp[i] == NULL) continue;
> >            if ( strncmp ( pv_tmp[i]->vg_name, pv_tmp[p]->vg_name,
> >                           NAME_LEN) == 0 &&
> >                 pv_tmp[i]->pv_number == pv_tmp[p]->pv_number &&
> >                 strncmp ( pv_tmp[i]->pv_uuid, pv_tmp[p]->pv_uuid,
> >                           UUID_LEN) == 0) {
> >               free ( pv_tmp[p]);
> >               pv_tmp[p] = NULL;
> >               goto pass_end;
> >            }
> >         }
> >
> >         if ( strcmp ( pv_tmp[p]->vg_name, vg_name) == 0) {
> >            if ( pv_number < pv_tmp[p]->pv_number)
> >               pv_number = pv_tmp[p]->pv_number;
> >            np++;
> >         }
> >pass_end:
> >      }
> >
> >
> >Gimme feedback if it works for you.
> >
> >Regards,
> >Heinz      -- The LVM guy --
> >
> >On Mon, Sep 25, 2000 at 04:52:40PM -0700, Tim Pepper wrote:
> >> I've set up a little test machine to play with lvm.  It's running RedHat 6.2
> >> with a 2.4-test8 kernel and lvm 0.8.
> >> 
> >> I've successfully created and used an lv (with a reiserfs filesystem on top
> >> of it).  My problem is that when I reboot the lv is gone.  vgscan finds
> >> nothing.  pvdisplay, lvdisplay and vgdisplay likewise show nothing.  If I go
> >> through the steps though to recreate the lvm, pvcreate seems to think
> >> something's there and wants me to do a '-ff'.  I can then continue on.
> >> 
> >> Playing around I see:
> >> 
> >> 	[root@qalab5 /root]# umount /mnt/nz
> >> 	
> >> 	[root@qalab5 /root]# lvdisplay /dev/netzero/big 
> >> 	--- Logical volume ---
> >> 	LV Name               /dev/netzero/big
> >> 	VG Name               netzero
> >> 	LV Write Access       read/write
> >> 	LV Status             available
> >> 	LV #                  1
> >> 	# open                0
> >> 	LV Size               34.18 GB
> >> 	Current LE            8750
> >> 	Allocated LE          8750
> >> 	Allocation            next free
> >> 	Read ahead sectors    120
> >> 	Block device          58:0
> >> 	
> >> 	[root@qalab5 /root]# vgscan
> >> 	vgscan -- reading all physical volumes (this may take a while...)
> >> 	vgscan -- no volume groups found
> >> 
> >> 	[root@qalab5 /root]# lvdisplay /dev/netzero/big 
> >> 	lvdisplay -- ERROR: VGDA in kernel and lvmtab are NOT consistent; please run
> >> 	vgscan
> >> 
> >> 	[root@qalab5 /root]# vgscan
> >> 	vgscan -- reading all physical volumes (this may take a while...)
> >> 	vgscan -- no volume groups found
> >> 	
> >> 	[root@qalab5 /root]# mount /mnt/nz
> >> 
> >> I can't seem to display it, but it does remount here.
> >> 
> >> I was thinking that maybe the 'vgchange -a n' shouldn't be done or perhaps I
> >> was doing it at the wrong time (at shutdown after the filesystem on the lv was
> >> umounted), but the above seems flakey even without vgchange in the picture.
> >> 
> >> Any ideas what could be going on?  Thanks in advance for any help.
> >> 
> >> Tim
> >> 
> >> --
> >> *********************************************************
> >> *  tim.pepper@opensales dot com     * Venimus, Vidimus, *
> >> *  http://www.opensales.com         * Dolavimus         *
> >> *********************************************************
> >
> >=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
> >
> >Heinz Mauelshagen                                 Sistina Software Inc.
> >Senior Consultant/Developer                       Bartningstr. 12
> >                                                  64289 Darmstadt
> >                                                  Germany
> >Mauelshagen@Sistina.com                           +49 6151 7103 86
> >                                                       FAX 7103 96
> >=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
> 

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

Heinz Mauelshagen                                 Sistina Software Inc.
Senior Consultant/Developer                       Bartningstr. 12
                                                  64289 Darmstadt
                                                  Germany
Mauelshagen@Sistina.com                           +49 6151 7103 86
                                                       FAX 7103 96
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

Re: [linux-lvm] lv not persistent across reboot?

[Mats Wichmann]

At 02:47 PM 09/27/2000 +0000, Heinz J. Mauelshagen wrote:
>
>Morning Steve :-{)
>
>On Wed, Sep 27, 2000 at 07:19:14AM -0500, Steve Brueggeman wrote:
>> Does this imply that Linux LVM will also have problems with discs in H.A.
>> configurations? 
>
>Yes.
>
>> 
>> For example: Fibre Channel drives have two ports on them.  If I have a
Linux box
>> with two Host Adapters, and each adapter is connected to the same set of
drives,
>> but on different ports, will v0.8final (without the patch below) have
unstable
>> vgscans?
>
>Yes, it should.
>
>> 
>> I have not been following the high availability mailing list, and a
solution may
>> already exist  there.  If so, and you know how, I'd be interested in a
quick
>> description.
>
>Not that i am aware of.

Does anybody have any experience to contribute about what other
LVM systems do in these situations?  They don't have the dynamic
scan/assignment stuff in Solaris or AIX, right?  (Showing my
ignorance here).

My experience of FC-AL setups is limited to theoretical at this
point, but I had been wondering how they are addressed by systems.
Is the dual-port stuff handled within the driver such that it's
not actually presented as two separate "devices"?  The presence
of two ports is a redundancy (+optionally performance) issue,
so that would almost make sense to me that one would hide the
physical reality inside the driver.

-- mats

Re: [linux-lvm] lv not persistent across reboot?

[Christoph Hellwig]

On Wed, Sep 27, 2000 at 02:47:14PM +0000, Heinz J. Mauelshagen wrote:
> > I have not been following the high availability mailing list, and a solution may
> > already exist  there.  If so, and you know how, I'd be interested in a quick
> > description.
> 
> Not that i am aware of.

One of the goals of my in-kernel scanning is that it should handle simple
multi-pathing correctly. The Kernel will try to sort out dublicated pv's.
But I doubt it will be ready soon enough for your project :(

	Christoph

-- 
Always remember that you are unique.  Just like everyone else.

Re: [linux-lvm] lv not persistent across reboot?

[Tom Dawes-Gamble]

Hi,

HPUX LVM will show both devices in the volume group.
One device will be the "Primary link" and the other the "Alternate link"
The lvm commands label the primary and alternate link so you know which 
is which.  There are also option to allow you to switch them around.
The primary is the first device added to the volume group.

All I/O is done to the primary link.  If however the I/O fails on the 
Primary link LVM will switch to the Alternate link and use that.
So if controler "A" goes bad you can still use the VG via Controller B.
Of course if the disk goes bad your dead in the water.

If you have two disks visible on the same two controllers then you 
can set one primary on controller A and the other primary on controller
B then if either controller fails you just loose bandwidth but you don't
stop.

If fact when the Primary goes bad it switches and becomes the
Alternate link and the Alternate becomes the new Primary link.

If you want more detail just let me know.

Tom.

On Wed Sep 27 16:55:31 2000 Mats Wichmann wrote:-
> 
> At 02:47 PM 09/27/2000 +0000, Heinz J. Mauelshagen wrote:
> >
> >Morning Steve :-{)
> >
> >On Wed, Sep 27, 2000 at 07:19:14AM -0500, Steve Brueggeman wrote:
> >> Does this imply that Linux LVM will also have problems with discs in H.A.
> >> configurations? 
> >
> >Yes.
> >
> >> 
> >> For example: Fibre Channel drives have two ports on them.  If I have a
> Linux box
> >> with two Host Adapters, and each adapter is connected to the same set of
> drives,
> >> but on different ports, will v0.8final (without the patch below) have
> unstable
> >> vgscans?
> >
> >Yes, it should.
> >
> >> 
> >> I have not been following the high availability mailing list, and a
> solution may
> >> already exist  there.  If so, and you know how, I'd be interested in a
> quick
> >> description.
> >
> >Not that i am aware of.
> 
> Does anybody have any experience to contribute about what other
> LVM systems do in these situations?  They don't have the dynamic
> scan/assignment stuff in Solaris or AIX, right?  (Showing my
> ignorance here).
> 
> My experience of FC-AL setups is limited to theoretical at this
> point, but I had been wondering how they are addressed by systems.
> Is the dual-port stuff handled within the driver such that it's
> not actually presented as two separate "devices"?  The presence
> of two ports is a redundancy (+optionally performance) issue,
> so that would almost make sense to me that one would hide the
> physical reality inside the driver.
> 
> -- mats
> 


-- 
char  *r,*e,*w="%.9s%.7s%.7s\n";extern int printf(const char*,...);int main(){
int l=*w,a,b,th=*(w-~(l/=l))-*(w+l);b=*w+~th--;a=b-th;//Aviation Briefing Ltd.
r=e="  DISPLAY'tmdg@avbr';,,;'ief.com'*>"+b;l+=~b,th-=printf(w,e-a,th+e,r);
r=e="  DISPLAY'http://www.avbrief.com/' *>"-~b,exit(~l-printf(w,e+~a,th+e,r));}