After you have done your backups to tapes, do you verify the content of the tapes ?
never
sometimes
always
The reason I am asking is that here in the office, all the backup procedures include verifying the content of the tapes (no matter if it is a savevg, mksysb or Tar). The only reason I can think of for doing this is that the tapes/drives here are not 100% reliable as we sometimes get errors on verifications (5-10% of the times). If they were 100% reliable, then I do not see why we would have to verify all the backups. It just adds up to the amount of work to do during those days.
Are you talking something like DDS/3? I'm not surprised. Newer technologies are more reliable and have better mechanisms for guaranteeing that the data is written accurately.
When I was doing ufsdump to DDS/3, I always used the option that verified the tape. In addition to that, I would test recover data periodically.
Now I'm using AIT5, and I'm using Amanda. I periodically check my backup procedures and recover some files to make sure things are working, but I don't run a verify every time.
Test recovery from media is always the most reliable way provided you can spare the time and equipment to do it.
It can be huge effort depending on what you want to recover.
Usually after 2-3years must replace backup media because they will start to degrade. Replacing media can be very expensive endeavor especially if you use things like LTO and your backups run into several hundred tapes, it can cost a small fortune.
Think this is covered by one of Murphy's laws. IIRC it states that the one file that is sure to corrupt is the one file that corrupted on your last backup. Or something.
I recognize that verification is a user of significate resources but unverified backups can't be trusted. You are playing "bet your business".
My customers are on SCO, not AIX, and their backups are verified then stored in two different places each night.
We are not using any options to verify the tape. We are manually doing a software reading test on the tapes to see if they are readable.
ex:
if a backup was done with Tar, we verity the tape with tar tvf
if a backup was done with mksysb, we do an lsmksysb on it
if a backup was done with savevg, we use smit option to list the tape content