--On Monday, October 06, 2003 06:36:41 +0100 Tony <td_miles AT yahoo DOT com> 
wrote:

> Hi Jon,
> 
> Thanks for the response.
> 
> Definitely DDS4 tapes (we have never had DDS drives before, so
> there is no possibility of old tapes getting mixed in).
> 
> I tried it without software compression (my first thought too),
> results were:
> 
> =============================
> 
> *** A TAPE ERROR OCCURRED: [[writing file: No space left on
> device]].
> Some dumps may have been left in the holding disk.
> Run amflush to flush them to tape.
> The next tape Amanda expects to use is: daily04mon.
> 
> FAILURE AND STRANGE DUMP SUMMARY:
>   qtechwas0  /var lev 0 STRANGE
>   qtechwas1  /opt lev 0 STRANGE
>   qtechwas2  /opt lev 0 FAILED [out of tape]
>   qtechwas2  /opt lev 0 FAILED ["data write: Connection reset by
> peer"]
>   qtechwas2  /opt lev 0 FAILED [dump to tape failed]
> 
> STATISTICS:
>                           Total       Full      Daily
>                         --------   --------   --------
> Estimate Time (hrs:min)    0:03
> Run Time (hrs:min)         2:32
> Dump Time (hrs:min)        1:58       1:58       0:00
> Output Size (meg)       20069.8    20069.8        0.0
> Original Size (meg)     20069.8    20069.8        0.0
> Avg Compressed Size (%)     --         --         --
> Filesystems Dumped           28         28          0
> Avg Dump Rate (k/s)      2905.8     2905.8        --
> 
> Tape Time (hrs:min)        2:07       2:07       0:00
> Tape Size (meg)         20070.7    20070.7        0.0
> Tape Used (%)              60.8       60.8        0.0
> Filesystems Taped            28         28          0
> Avg Tp Write Rate (k/s)  2704.0     2704.0        --
> 
> =============================

So what was on the 'taper' line of the report ?  It should look
something like:
taper: tape archive07 kb 43505184 fm 23 [OK]   (from one of my reports)
which tells you how many bytes and images were successfully written
to tape.


> 
> So it couldn't even fit 20 GB of uncompressed data onto the tape
> ?

Is the dump going to a holding disk and then streamed to tape, or
as it looks like from the times, going straight to tape?  If the
latter, if it isn't dumping fast enough the tape might be catching
up and shoe-shining as it constantly backspaces and starts over.
That can waste a lot of tape as well as being slow.

Frank

> My info on there being no jumpers to set compression is from the
> manual. I suspect that you could be correct in suggesting there
> might be DIP switches on the underside of the drive, as I have
> commonly seen this too. Unfortunately is is hard for me to
> schedule downtime to physically extract the tape drive to look
> at, but I will try to get time for this and see what I find.
> 
> The "mt" command is supposed to show compression state, but when
> I attempt this I get nothing. EG.
> 
> [root] # /bin/mt -f /dev/st0 compression
> [root] # /bin/mt -f /dev/st0 compression on
> [root] # /bin/mt -f /dev/st0 compression
> [root] # /bin/mt -f /dev/st0 compression off
> [root] # /bin/mt -f /dev/st0 compression
> [root] # 
> 
> Note the absolute lack of any output after using the command,
> regardless of whether I try to turn compression on/off or just
> display compression status. The MAN file for mt says:
> 
> ===============================
>  compression
>             
>   (SCSI tapes) The compression within the  drive  can
>   be  switched  on  or  off  using  the MTCOMPRESSION
>   ioctl. Note that this method is  not  supported  by
>   all  drives implementing compression. For instance,
>   the Exabyte 8 mm drives use density codes to select
>   compression.
> ===============================
> 
> so it may be that it doesn't support this option (unfortunately
> !).
> 
> 
> So I'm still looking for answers....   :(
> 
> 
> 
> regards,
> Tony.
> 
> 
>  --- Jon LaBadie <jon AT jgcomp DOT com> wrote: 
> 
>> 
>> That looks to be the problem, unless ???
>> I'm surprised HW compression expands it that much.
>> 
>> You are using DDS-4 tapes, not DDS-{123} ones right?
>> 
>> Try it next run without software compression.  25GB should
>> have
>> no trouble fitting.  HW compression will take it down to about
>> the same 15GB that gzip did.
>> 
>> I think some mt versions have commands that show the
>> compression
>> state.  And commands to turn it off too.
>> 
>> Most drives would come with compression on as the default.
>> 
>> My drive (HP DDS-3) has DIP switches affect the defaults.
>> One controls which state it comes up in after at power up.
>> The other says whether it can subsequently be changed by
>> a software command.  For a while I did not think it had
>> any switches or jumpers to affect compression.  Then I
>> found out you have to remove the drive from the case to
>> access them.
>> 
>> -- 
>> Jon H. LaBadie                  jon AT jgcomp DOT com
>>  JG Computing
>>  4455 Province Line Road        (609) 252-0159
>>  Princeton, NJ  08540-4322      (609) 683-7220 (fax) 
> 
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