[Info-vax] Backup verify problems

[Richard B. Gilbert]

DJ wrote:
> On Jan 30, 3:26 pm, gsdguy <peter... at chem.washington.edu> wrote:
>> I am getting backup verify errors and I don’t know why. I hope someone
>> can explain what is happening.
>>
>> I had a disk and tape drive failure and restore the disk from a backup
>> tape ( I bought a new DAT tape drive). I decided to start using the /
>> verify switch when I do backups. When I did my first backup to tape
>> with /verify I got verify errors like the ones shown below.
>>
>> %BACKUP-E-VERIFYERR, verification error for block 31 of DUA2:[LEROY]
>> MAIL.MAI;1
>> %BACKUP-E-VERIFYERR, verification error for block 32 of DUA2:[LEROY]
>> MAIL.MAI;1
>> %BACKUP-E-VERIFYERR, verification error for block 33 of DUA2:[LEROY]
>> MAIL.MAI;1
>> %BACKUP-E-VERIFYERR, verification error for block 34 of DUA2:[LEROY]
>> MAIL.MAI;1
>> %BACKUP-E-VERIFYERR, verification error for block 35 of DUA2:[LEROY]
>> MAIL.MAI;1
>> %BACKUP-E-VERIFYERR, verification error for block 36 of DUA2:[LEROY]
>> MAIL.MAI;1
>>
>> I created a disk backup saveset and got the same verify errors. I
>> checked the error log for any hardware errors and there were no
>> errors. I then restored one of the files that had verify errors to
>> another disk and did a difference between the original file and the
>> restored file. The difference program said that there was no
>> difference between the two files. I also did an analyze/disk on the
>> disk drive and there are not errors.
>>
>> Can someone explain what is going on? How can I get rid of these
>> verify errors? Thank you.
> 
> Dear GSDGUY:
> 
> Backing and verifying on any volatile file will cause this problem. At
> time = 0, you backup the email file, then at time = 2 hours you are
> verifying what you back up onto tape. However, during this time
> “Leroy” has deleted some email messages, thus causing the backup
> verification error to occur. The information store in the mail.mai
> file has been deleted.
> 
> Regards,
> Daryl Jones

If you can't, somehow, quiesce the system, or at least the disk, while 
you make your backup, you may not be able to restore everything in 
usable form!

Databases, e.g. Oracle, can sometimes make a "snapshot" of a filesystem 
that allows you to get a consistent backup.  Lacking such a feature, 
your choices are to take the disk offline or to live with the 
possibility that something will be lost if you have to do a restore.