Topic: SCSI Tape Drive Detected - nst0 No Device !

[Graham]

Hi All,

I am in the office for another hour and was wondering if anyone reading this could give me some pointers ?

Tape backups where working great for about a month. After a freeze and subsequent re-boot I lost backups and keep getting email reminders about tape not being loaded etc

The command mt -f /dev/nst0 tell or status renders :-

/dev/nst0 : No such Device

Anyone had this problem and resolved it ?

Is nst0 a sym link to another devive file ?

Any immediate help greatly appreciated !

Regards

Graham

[Graham]

The device file nst0 does actually exist in /dev

In the Linux Tape Reference is says that if no valid response is found
then the st.o device is not preoperly loaded ?

How can I check this ?

I will hunt around and try and find the modules and how to load them !

[Des Dougan]

Graham,

Look into the boot message log (dmesg | more). In mine I see the following:

(scsi0) found at PCI 0/10/0
(scsi0) Narrow Channel, SCSI ID=7, 3/255 SCBs
(scsi0) Cables present (Int-50 YES, Ext-50 NO)
(scsi0) Downloading sequencer code... 415 instructions downloaded
scsi0 : Adaptec AHA274x/284x/294x (EISA/VLB/PCI-Fast SCSI) 5.1.33/3.2.4
       
scsi : 1 host.
  Vendor: Seagate   Model: STT20000N         Rev: 6A51
  Type:   Sequential-Access                  ANSI SCSI revision: 02

This is the system recognizing the adaptor for my tape drive. From what you said, I'd guess that this may not be there. I would shutdown the box and check the connections - something may have worked itself loose.


Des Dougan

[Graham]

I checked dmesg also on the IBM Netfinity you can do a diagnostic from ROM and scan the scsi bus. It picks up 3 : Adapter / HDD / Tape Device

As a side I have also tried :-

/sbin/insmod st

Which reported that a module with the name st already exists . . .

[Graham]

Here is dmesg output :-

(scsi0) found at PCI 0/6/1
(scsi0) Wide Channel B, SCSI ID=7, 32/255 SCBs
(scsi0) Downloading sequencer code... 383 instructions downloaded
(scsi1) found at PCI 0/6/0
(scsi1) Wide Channel A, SCSI ID=7, 32/255 SCBs
(scsi1) Downloading sequencer code... 383 instructions downloaded
scsi0 : Adaptec AHA274x/284x/294x (EISA/VLB/PCI-Fast SCSI) 5.1.33/3.2.4
       
scsi1 : Adaptec AHA274x/284x/294x (EISA/VLB/PCI-Fast SCSI) 5.1.33/3.2.4
       
scsi : 2 hosts.
(scsi0:0:4:0) Synchronous at 40.0 Mbyte/sec, offset 8.
  Vendor: IBM-PCCO  Model: DGHS09Y       !#  Rev: 0420
  Type:   Direct-Access                      ANSI SCSI revision: 03
Detected scsi disk sda at scsi0, channel 0, id 4, lun 0

15 minutes until alarm set / lockout . . .

[Graham]

Output of cat /scsi

[root@server log]# cat /proc/scsi/scsi
Attached devices:
Host: scsi0 Channel: 00 Id: 04 Lun: 00
  Vendor: IBM-PCCO Model: DGHS09Y       !# Rev: 0420
  Type:   Direct-Access                    ANSI SCSI revision: 03
Host: scsi0 Channel: 00 Id: 14 Lun: 00
  Vendor: SDR      Model: GEM200           Rev: 2
  Type:   Processor                        ANSI SCSI revision: 02
[root@server log]#

Any help guys . . . .

[Graham]

Hi,

I have trawled the forums and am going dizzy. Also I am getting worried as there have been no successfull backups for several weeks now . . .

I cant seem to find a similar problem and am not sure where to go next other than a complete re-install which means I will have to back up to one of the client HDD's. This seems like drastic measures really.

It looks like :-

SCSI BIOS sees the drive
st.o is loaded correctly
/dev/nst0 exists

Hmmmmm . . . .

[Graham]

One thing I forgot about and havent mentioned so far :-

Early on before I put the server to work I installed the Backup Now
module.

This never worked for some reason and I forgot about it.

Do you think this may have clobbered the backup script somehow and hasnt become apparent until re-boot ?

Thanks for any morsels of information . . .

[Des Dougan]

Graham,

I don't know about Backup Now (or what it consists of), but I would take it out and see where that leaves you.

With reference to the last but one posting - if the drive was previously working, then I would expect to see /dev/nst0 even if something had happened in the interim, unless you had rebuilt the server (and I don't remember you saying you'd done that). If the SCSI adapter is OK, but the drive is faulty (or a connection is bad), then that would be one explanation for your problem. Did you check the connections? Boot with the drive disconnected from the adapter. Does /dev/nst0 still get identified?

Sorry I can't think of anything more right now.


Des Dougan

[Graham]

Des, Thanks for your reply. I didnt re-install.

I am reluctant to anyway as it took me so long to get to the bottom of the
mail collection problem and I dont want to fix one thing but end up with something else to try and sort out. Worst of it is, the server is in an office 20 miles away so you can appreciate the dillema !

Last time I checked mt -f /dev/nst0 still throws up a No Device' error.

Seems like the machine can see the drive at the hardware level, the drivers [kernel] can see it, the st module is loaded but somehow there is no link to the drive relating to nst0 ?

As I am only a newbie [relatively] I am finding this a bit tough - I have done all the checks I can find on the forums still to draw a blank - unless of course there is something staring me in the face and others are just waiting for the penny to drop ? This has happened on occasion and I know my self that sometimes if you leave people to figure it out just a little bit longer they get it sorted. That is, if they havent given up !!!

Thanks for replying anyway. If there is anything else you can think to check let me know. I must admit I never got round to just unplugging and reconnecting the drive - and of course there is a possibility it is faulty  . . . . but I am guessing I would get a different set of errors than this ?

[Graham]

If you have a problem similar to this please do the following first :-

1) Take the lid off your server
2) Unplug the data and power connectors
3) Plug them back in making sure they are in correctly and firmly

I spent nearly 8 hours trying to resolve this including doing a full
re-install !!!! It wasnt software but a hardware problem.

One thing that fooled me is that your SCSI Bios will not always
identify the device with its model / manu name / number.

I *thought* that the tape drive *was* being detetected when in fact
it was the redundant scsis bay device.

Once I had done the above the drive was detected and all now working !!!

A few things I learnt from this :-

a) Sometimes you over look the simple things. Try them first !

b) Heat / Dust / Oxidistion can cause a connector to be unreliable.
Even remaking the connection can clean it. [You could also try Servisol]

c) If you find an answer to something even by trial and error please come back here and report what you found - its helpfull for others and avoids threads that just drop off into nothing . . . .

Thanks !