Problems with dump/capacity/DLT IV 40-80GB Tape cartridges

[Gunther Schadow]

Hi Nathan,

Nathan Vidican wrote:
> I am trying to make use of dump to backup several volumes to a DLT IV tape 
> drive. I am using a Dell PowerEdge 110T, which contains a single DLT IV 
> 40/80GB tape drive unit attached to the external connector of an Adaptec 
> 3940UW pci-scsi host adaptor. 

> The tape drive is at ID 1, the controller at 
> ID 0, and there are no other devices attached to this controller. 

Not that it has anything to do with your problem, but isn't that a
rather non-canonical use of SCSI unit ids? I thought the standard was to
have the host adapter be the highest id, and disks be 0, 1, upwards
and tapes be second-to-highest downwards. This actually makes
sense if you think about it: the bios boot code will grab disks
from unit 0 upwards to try booting from there, if there is a tape in
the middle this may screw up your unit numbers. It's not a major issue.

> sa0 at ahc1 bus 0 target 1 lun 0 
> sa0: <BNCHMARK DLT1 391B> Removable Sequential Access SCSI-2 device 
> sa0: 20.000MB/s transfers (10.000MHz, offset 8, 16bit) 

looking good, besides the abovementioned minor issue

> When using 'dump -0au -f /dev/sa0 /server' I cannot fit the contents of 
> /server (approx 4.2gigs of data) onto a single tape volume. The tape 
> inserted is a brand new HP C5141F, (which is a 40/80GB DLT IV cartidge). 
> Dump prompts for a new tape to be inserted to complete the operation. I 
> assumed this had to do with the '-a' part in the dump command; assuming that 
> dump is therefore not (properly) auto-detecting the EOT (end of tape), or 
> using the wrong recording density and reaching the end of the tape all too 
> quickly. Using 'restore -i' I can indeed read the data written to the tape, 
> so it is writting the data... just not properly. 

Are you sure your drive actually operates at highest density?
It could be that it is set to DLT III size. Hmm, even there it
should be able to do several gigabytes. May be yours can write
TK50 or TK70 formats, which amount to less than 250 MB. Check your
LEDs on the drive (if any) what they say about density.

> The Question: 
> ~~~~~~~~~~~~~ 
>  
> Is anyone out there using similar hardware, or know of the proper arguments 
> to pass to dump to make full use of the capacity of these DLT IV cartridges? 
> I have checked HP's website, and these particular cartidges list a length of 
> 557Meters, and a density of 46.8K/80K/96K dependant upon 40GB/70GB/80GB 
> compression schemes. How do I formulate the dump command to properly make 
> use of these tapes.... any suggestions? 

dump -a should work. Check with your LEDs and/or mt for the density
modes you may have erroneously selected. Any jumpers to configure the
thing perhaps? The tape length calculation of dump is antiquated (and
very nice for that matter, since I do deal with 9-track reels.) Even
if you tell it you have a super long tape, if your drive reports end-
of-tape, dump will not be able to write any more. With the compression
that's going on in the DLT IV drives, the length calculation would at
best be approximate anyway.

regards
-Gunther

-- 
Gunther Schadow, M.D., Ph.D.                    gschadow at regenstrief.org
Medical Information Scientist      Regenstrief Institute for Health Care
Adjunct Assistant Professor        Indiana University School of Medicine
tel:1(317)630-7960                         http://aurora.regenstrief.org