StoreEver Tape Storage

Problems when I try to copy tapes.

John Th
Occasional Contributor

Problems when I try to copy tapes.

We have data stored on several tapes LTO-3 800GB (400GB nominally). We used for this the StorageWorks Ultrium 920 device. The 'data' is formed mainly from PNG images and AVI films, thus the compression engine was turned off.

Now we want to make a 2nd copy of these tapes, but we see that the 2nd copy is somewhat larger (we see it from the amount of free space on the 2nd tape reported by the Data Protector) and sometimes it doesn't fit on the 2nd tape. (The program asks for another tape).

The copy procedure is as follows:
1. Restore the 1st tape on an empty 500 GB disk. (note that the data on disk is sensibly smaller than 400 GB)
2. Backup the disk on the 2nd tape

We tried with compression turned on and off. If the compression is turned on then the results are slightly better, but still the 2nd copy is bigger and sometimes doesn't fit.

Personally I suspect that this is due because the catalog is also saved on tapes. (when we did the 1st series of copies, the catalog was smaller).

Can someone help us?