Sony DDS3 low capacity per tape

[regald]

Hi.

 

We're running a Sony SDT-D9000 (external SCSI, DDS3):

 

http://www.storagebysony.com/products/productmain.asp?id=120

 

connected to: Adaptec 2906, PowerMac G4, Mac OS X Server 10.3.6, Retrospect 6.0.204, rdu 6.0.

 

 

The 125 m DDS3 data cartridges should be able to store 12 GB uncompressed, and up to 24 GB using 2:1 hardware compression.

 

But, trying to backup to that drive, Retrospect reports a full tape after about 6 to 7 GB, and requests an additional tape. The tape is brand new, has been erased, etc.

 

 

Any idea what to do?

Thanks in advance for any advice.

 

 

Hannes

[hmseiden]

Hannes,

 

I have two recommendations. Sounds like the hardware compression isn't enabled or something else is interfering.

1. Check to see if hardware compression is enabled. Check the Backup Set in Retro (Configure>Backup Sets>Configure>Summary) to be sure Retro see this is enabled (and software compression is not on, see the next paragraph). Your drive may have come with info on how to do this or you will need to check with Sony. Perhaps someone else here on the list can give you specific guidance on this matter.

 

The drive could be set on by default, not settable at all, or a switch setting is required to be enabled. You may only think that hardware compression is enabled. Retro has to know about the hardware compression or it'll report wrong. If you're good at math you can calculate this figure from the MB/min speed reported by Retro.

 

2. You'll never use software compression, so uncheck this box in Retro if it's checked (Configure>Backup Sets>Configure>Options). Both this setting and the one above go with the Backup set. Changes to the compression settings may require you to make a new set.

 

While I think you should do somewhat better than you reported, you won't get (nor should you expect to get) 24GB transferred from your HD onto each filled tape. Heavily compressed files will require more space on the backup than others, for example.

 

Another reason your calculations may be wrong. You are going from a random access storage (HD) to a linear storage medium (tape), so adding incremental data to an existing backup will add to the amount of tape used.

 

These topics are discussed on the Dantz Knowledgebase. Some have been mentioned here on these forums. There is overhead in Retro backup process even if you don't use the software compression check box in Retro. I use a different tape media (AIT) and my data per tape is about 70% (35GB for a 50GB tape rated with hardware compression). Notice in all the Sony literature they say "...up to 12 GB." Your results _will_ vary!

 

Your Adaptec 2906 may be giving you hardware troubles but that may just slow you down instead of corrupt the data or change the storage used. However you should know that OS X and Adaptec have issues.