Hi TSM-ers!
We are using two kind of virtual tape solutions. The old solution is based on 
the DL4100 from EMC, the new solution is based on the DataDomain form EMC.
Because we are using them as a virtual tape server one is also bound to the 
shortcomings of the tape protocol. If there is some kind of hick-up or 
congestion during the data transfer, there is no retry, the I/O just fails. I 
have seen multiple cases where migrations were temporarily saturating the fiber 
adapters of the Data Domain server or one of the switches in between and this 
caused an write I/O error. This resulted in a corrupted virtual tape which I 
think this is strange. If TSM is moving data from the diskpool to a tapepool 
and this I/O fails and results in an I/O error, why does it delete that data 
from the diskpool? The data block move should be rolled back is such a case, 
right?
In the case where we are using the DL4100 we are using a primary and a 
copypool. Most of the times the data which is lost was backed up earlier by the 
backup stgpool of the diskpool and thus can be restored from the copypool, but 
in the DataDomain situation we use the DD replication and then the data on the 
corrupted tapes is gone forever!
Thanks for any clarification in advance!
Kind regards,
Eric van Loon
AF/KLM Storage Engineering
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