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Unexpected busfree in Message-out 10 May 2000
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Today I was installing three (yes three!) SCSI drives in my new webserver.  These were for additional storage, and were not going to be boot disks.  It is quite straight forward to add new disks.  You can usually get the system up and running in only the time it takes to install the disks.  Unfortunately, that was not the case for me.
The symptoms and the solution
But when I started the box, I saw these errors during the boot up:
Waiting 15 seconds for SCSI devices to settle
(probe1:ahc0:0:1:0): Unexpected busfree in Message-out phase
SEQADDR == 0x153
(probe2:ahc0:0:2:0): Unexpected busfree in Message-out phase
SEQADDR == 0x153
(probe1:ahc0:0:1:0): Unexpected busfree in Message-out phase
SEQADDR == 0x153
(probe2:ahc0:0:2:0): Unexpected busfree in Message-out phase
SEQADDR == 0x153
(probe1:ahc0:0:1:0): Unexpected busfree in Message-out phase
SEQADDR == 0x153
(probe2:ahc0:0:2:0): Unexpected busfree in Message-out phase
SEQADDR == 0x153
(probe1:ahc0:0:1:0): Unexpected busfree in Message-out phase
SEQADDR == 0x153
(probe2:ahc0:0:2:0): Unexpected busfree in Message-out phase
SEQADDR == 0x153
(probe1:ahc0:0:1:0): Unexpected busfree in Message-out phase
SEQADDR == 0x153
(probe2:ahc0:0:2:0): Unexpected busfree in Message-out phase
SEQADDR == 0x153
Mounting root from ufs:/dev/ad0s1a
da0 at ahc0 bus 0 target 3 lun 0
da0: <SEAGATE ST31230N 0300> Fixed Direct Access SCSI-2 device 
da0: 10.000MB/s transfers (10.000MHz, offset 15), Tagged Queueing
                                                          Enabled
da0: 1010MB (2069860 512 byte sectors: 64H 32S/T 1010C)

On startup, only one drive (da0) was found.  This was strange.  I decided to concentrate on the above messages first.  I searched the mailing list archives at the FreeBSD site and found a couple of references to unterminated SCSI chains.  For more information on that topic, please read Storage Devices in the FreeBSD Handbook.  That would be easy to fix.  I checked each drive for correct termination, found the problem, and made sure the correctly terminated drive was furthest on the cable from the SCSI card.

But I could still find only one drive.  So I decided to try each disk one at a time.  So I tried this pattern:

  1. connect one SCSI drive
  2. boot the box.
  3. It would find the drive.
  4. goto step 1 and try another drive

Each drive could be found if used alone.  Then I tried two drives together.   Still only one drive would be found.  And it was always the drive closest to the SCSI card.  Hmmm, I began to suspect the cable.  So I grabbed the cable which was supplied with the SCSI card.  That was successful.  It found all the drives.  Unfortunately, that cable had enough connectors for only two drives.   The original cable had room for four.  Luckily, I was able to get a cable from a friend who just happened to have one.

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