tape drive problem

[Vu Pham]

Bill Campbell wrote:
> On Sat, May 31, 2008, Vu Pham wrote:
>>
>> Vu Pham wrote:
>>> My tape drive suddenly reports the following error when I write to it.
>>>
>>> tar: /dev/st0: Cannot open: Read-only file system
>>>
>>> What can cause this ? I used a tape cleaner tape to clean it but it does 
>>> not fix. And the "dirty" LED is not on.
>>>
>>> It is a DLT1 tape drive.
>>>
>> More :
>>
>> [root at pepper3 log]# mt -f /dev/st0 status
>> SCSI 2 tape drive:
>> File number=0, block number=0, partition=0.
>> Tape block size 0 bytes. Density code 0x1a (DLT 20GB).
>> Soft error count since last status=0
>> General status bits on (45010000):
>> BOT WR_PROT ONLINE IM_REP_EN
>>
>> It says "WR_PROT". That's why tar cannot write to it. But why ? Hardware 
>> problem ?
> 
> My guess is that you have engaged the tape's write-protect.
> 
> Most mag tapes have some method to write-protect them, the method
> depending on the type of tape.  It's been a while since I looked
> a tapes, but as I remember the DDR DAT style tapes have a little
> slide at the back of the cartridge.  The 1/4in tapes such as the
> DC600s have a rotating mechanism on the front side (towards the
> heads), etc.
> 

Thanks, Bill. I checked that on three tapes  randomly out of  31 tapes 
which I am using for daily backup of this system.


Vu