Dropped interrupts

[Justin T. Gibbs]

On Jan 30, 2014, at 3:21 PM, Ben Laurie <ben at links.org> wrote:

> On 26 January 2014 22:46, Justin T. Gibbs <gibbs at scsiguy.com> wrote:
>> On Jan 26, 2014, at 1:52 AM, Ben Laurie <ben at links.org> wrote:
>> 
>>> On 25 January 2014 17:15, Justin T. Gibbs <gibbs at scsiguy.com> wrote:
>>>> On Jan 24, 2014, at 10:44 PM, Ben Laurie <ben at links.org> wrote:
>>>> 
>>>>> Aha, finally got the error again...
>>>> 
>>>> I don't know enough about your backup or Bacula to know if this is amount that should be written, but we attempted a write in variable block mode of 64512 bytes.
>>> 
>>> I don;t think there's anything wrong with that. Not at the machine
>>> right now, but I think that's actually the default max block. No idea
>>> why.
>>> 
>>>> The command, data transfer list, and controller state are all consistent with this.  The command was successfully transferred to the tape drive, but it never transitioned to data phase to allow us to begin the data transfer.  (In parallel SCSI, the target controls all state transitions).
>>>> 
>>>> Since there are no parity errors or other indications of a transport error, my hunch is that this is a tape drive issue.  Are you running the latest available firmware for it?
>>> 
>>> No idea, its a very old LTO-2 drive. I'll see if I can find an update.
>>> 
>>>> How many write cycles do you have on your media?
>>> 
>>> I have seen this error on brand new media. I'd guess the most cycles
>>> any tape has had is around 10.
>>> 
>>>> When was the last time you cleaned the drive?
>>> 
>>> LTO drives are self-cleaning. So ... never.
>> 
>> This is a popular misconception.  LTO drives include brushes deployed during load or unload to remove large particle contamination off the head.  This increases the time interval between traditional cleanings, but doesn't make them unnecessary.  Certain LTO drives will tell you (e.g. light a LED) when they require cleaning, but I don't know if this is one of them.  There have also been firmware bugs on some drives that prevent the cleaning indicator from working as expected.
>> 
>> If the drive has over 500 hours on it, I would suggest a cleaning pass.
> 
> Are you suggesting that a need for cleaning could cause this problem?

I can’t say why the drive isn’t responding.  But if it hasn’t been cleaned since it was manufactured, you are probably getting less data per tape than optimal, slower transfer speeds than optimal, or both.

I don’t know if the LTO-2 model listed on this page is the same as what you have, but if it is, there were several firmware releases after 3AYC:

http://www-01.ibm.com/support/docview.wss?uid=ssg1S4000055

—
Justin