03-23-2006 09:06 PM
I have been trying to find information on the WORM aspect of LTO 3 tape drives.
As far as I can see this is accomplished by the Cartridge Memory (CM) chip in the tape cartridge and some low level encoding on the tape itself which gives you the ability to append data to the tape but not overwrite the original data, presumably by modifying only the low level encoding where the tape has been written?
Can anyone point me at a public source of information that provides more information on this?
Thanks in anticipation,
03-26-2006 10:11 AM
* The CM (cartridge memory) uses a unique cartridge type for WORM which cannot be modified. The drive immediately knows it's a WORM tape as soon as it's loaded.
* Key WORM ID information is written into the first dataset on tape which is picked up by the drive as soon as any write/read/space command is received.
* Additional WORM ID information is written into *every* dataset (each 1.6MB of data) written to tape.
* The WORM ID information is made up of a combination of parameters that cannot be reconstructed outside the drive. This is to prevent tampering.
* WORM specific information is encoded in the servo code by the manufacturer of the tape. This data cannot be modified.
* The HP drives check all of the above every dataset and also at EOD. Any tampering will be identified immediately and an appropriate error returned.
I hope this is useful. If I come across an official document I'll let you know.
03-28-2006 01:15 AM
This takes you to the website of the Ultrium consortium which hosts the format specs and agreements. The white paper you want is number (3) and you'll need to register your name, company and email address to view it.
It's a pretty thorough document (I've just taken a look) and should answer all your questions.