Re: Pb with external RAID controller in lk 2.4

[Patrick Mansfield <patmans@us.ibm.com>]

On Wed, May 22, 2002 at 09:49:01AM +0200, Fabien Salvi wrote:
> Fabien Salvi wrote:

> > May 17 16:19:36 node01 kernel: Attached scsi disk sda at scsi0, channel
> > 0, id 0, lun 0
> > May 17 16:19:36 node01 kernel: Attached scsi disk sdb at scsi0, channel
> > 0, id 0, lun 1
> > May 17 16:19:36 node01 kernel: Attached scsi disk sdc at scsi0, channel
> > 0, id 0, lun 2
> > May 17 16:19:36 node01 kernel: Attached scsi disk sdd at scsi0, channel
> > 0, id 0, lun 3
> > May 17 16:19:36 node01 kernel: Attached scsi disk sde at scsi0, channel
> > 0, id 0, lun 4
> > May 17 16:19:36 node01 kernel: Attached scsi disk sdf at scsi0, channel
> > 0, id 0, lun 5
> > May 17 16:19:36 node01 kernel: Attached scsi disk sdg at scsi0, channel
> > 0, id 0, lun 6
> > May 17 16:19:36 node01 kernel: Attached scsi disk sdh at scsi0, channel
> > 0, id 0, lun 7
> > May 17 16:19:36 node01 kernel: Attached scsi CD-ROM sr0 at scsi2,
> > channel 0, id 5, lun 0
> > May 17 16:19:36 node01 kernel: sym2:5: FAST-20 SCSI 20.0 MB/s ST (50.0
> > ns, offset 16)
> > May 17 16:19:36 node01 kernel: sr0: scsi3-mmc drive: 17x/40x cd/rw
> > xa/form2 cdda tray
> > May 17 16:19:36 node01 kernel: Uniform CD-ROM driver Revision: 3.12
> > May 17 16:19:36 node01 kernel: sym0:0: FAST-20 SCSI 20.0 MB/s ST (50.0
> > ns, offset 16)
> > May 17 16:19:36 node01 kernel: SCSI device sda: 17776640 512-byte hdwr
> > sectors (9102 MB)
> > May 17 16:19:36 node01 kernel: Partition check:
> > May 17 16:19:36 node01 kernel:  sda: sda1 sda2 sda3 sda4
> > May 17 16:19:36 node01 kernel: SCSI device sdb: 17776640 512-byte hdwr
> > sectors (9102 MB)
> > May 17 16:19:36 node01 kernel:  sdb: sdb1
> > 
> > Like you can see, it founds 8 disks !
> > I tried to increase max_scsi_luns to 64 to see if it will find as many
> > disks as luns, but it does not go after lun7 ==> 8 disks
> > 

> Gérard and Doug, thanks for your help.
> 
> But, in fact, after re-reading my email, I've seen it's confusing
> because I didn't explain correctly the problem.
> 
> The lk 2.2 has the good comportment : it only finds the 2 disks.
> And, that's ok, I have really only 2 disks to be seen.
> 
> The problem is with the 2.4 kernel that finds 8 disks but it should only
> see 2 disks, because there is only 2 disks !
> 
> The other disks are not accessible :
> $fdisk /dev/sdc
> 
> Unable to open /dev/sdc
> 
> It's the same from sdc to sdh...
> 
> 
> I've tried in the 2.4 kernel to increase the max_scsi_luns because I
> thought lk may find as disks as many luns I have, but it's not the case
> : it don't find more than 8 disks (maybe this is reassuring...).
> 
> So here is the problem : the lk 2.4 finds more disks than I have !

The 2.4 kernel won't scan past LUN 7 for SCSI-2 devices - you can try
modifying the code and set the max to 31 in scsi_scan.c.

The device is probably setting the peripheral-qualifier (PQ) such that the
scan continues but the device is marked offline, this is just annoying
if do not have a lot of them. In scsi_scan.c:

        /* Use the peripheral qualifier field to determine online/offline */
        if (((scsi_result[0] >> 5) & 7) == 1)   SDpnt->online = FALSE;
        else SDpnt->online = TRUE;

The above means that sd will attach to the device, but won't try to read
capacity etc, and an open of the device will fail. Redhat kernels have
some changes to avoid this problem, there was also a PQ patch posted
some time ago (it would make sense to put it into 2.5, especially now that
the inquiry data is retained, and avoid setting online to FALSE).

There is also some odd case (AFAIR when initializing sd after the adapter has
been loaded and scanned the devices) where the online gets reset to TRUE
and causes sd.c to fail trying to read the non-existent LUN.

-- Patrick Mansfield
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