[Info-vax] Getting tape drive errors make no sense

[tadamsmar]

I tried to copy a large save-set (a full disk backup) from tape to a large disk.  That is I am just trying to copy the file from tape to disk, not trying to restore a volume.

The save-set was created and verified on a DDS3 tape on a DDS3 drive. One of those 12/24 GB DAT drives that are common on Alpha DS10 466 mhz systems.

I was trying to copy it using a DDS4 hotswap drive on a Alpha DS10 617 mhz system.

Both systems have disk shadow sets with 2 members.

I got errors when I tried to copy.

I did a search of the file and also got parity errors.

I tested the tape on a 3rd system with a DDS3 drive (similar system that wrote the tape).  I could search it there with no errors.

(I was using searching instead of copying as a test case because the 3rd system did not have big disks that would allow copying the whole file.)

The DDS4 drive is backward compatible to DDS3. I does incrementals every night to a DDS3 tape and it's disk backups are done with DDS3 tapes.  I cleaned the drive after the errors, but it shows no need be cleaned when it does the incrementals.

I will probably see if the DDS4 drive can search one of the savesets that were created on it on Monday.  Maybe I need to do this kind of stress test to sort things out.

Some of my tests indicate that it's not hitting the parity errors at the same point on the tape.  I tried copying the file twice and it got farther the second time before it had a parity error.