On Wed April 23 2003 11:42, Paul Bijnens wrote:
>T. Blader wrote:
> >...
>
>You already got a perfect explanation from Mich Collinsworth, but
>
> > ...
>>
>> Avg Dump Rate (k/s)       255.9      231.5      443.2
>> Avg Tp Write Rate (k/s)   269.7      239.2      551.8
>>
>> ...
>>   taper: tape TECH14 kb 10454688 fm 23 writing file: short write
>
>I don't know any tapedrive that has a capacity of 10.5 Gbyte.
>(Well to be honest, I only know the cheaper tape drives.)
>
>Is this, just guesssing, a DDS-3 drive with a capacity of 12
> GByte? If yes, could it be that you have hardware compression on?
> I would expect to run into EOT at about 11.5 Gbyte.  Putting
> compressed files on a tape with hardware compression on expands
> the data!

And I'd guess that the 10.5 gigs was about right if hardware 
compression is on.

>The latest amanda 2.4.4 has a program "amtapetype" that detects
>the hardware compression settings of a drive.  (It's time to
> upgrade anyway :-)

Thats 'tapeinfo' Paul. :-)  amtapetype checks the tape in the drive 
for its actual capacity, and since it uses /dev/urandom as its data 
source, it won't get very close to 12 gigs if the hardware 
compressor is on.

Also, tapeinfo seems to want to access the drive thru the sg 
interface, not the nst0 interface, so here, even though amanda is 
using /dev/nst0, tapeinfo needs a -f /dev/sg0 for the drive, and a 
-f /dev/sg1 to report on the changer.  A bit odd, but thats how it 
works.  So those without the sg device compiled, may not be able to 
use tapeinfo.

To allow amanda to have a good view of the tape, and because gzip 
can compress better than the hardware, sometimes by large amounts, 
its generally recommended the drives compressor be shut off 
permanently by this group.  It less amanda hassle in the long view.

If you are constantly overrunning the tape, then its time to extend 
the dumpcycle and runspercycle, giving amanda more days to stuff x 
amount of data away.  And that implies a longer tapecycle (more 
tapes) in order to maintain the recomended minimum of at least two 
full backups on hand, and don't count the tape thats in the drive.  
If that write session should fail, you should still have 2 full 
backups on hand.

-- 
Cheers, Gene
AMD K6-III@500mhz 320M
Athlon1600XP@1400mhz  512M
99.26% setiathome rank, not too shabby for a WV hillbilly
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Copyright 2003 by Maurice Eugene Heskett, all rights reserved.