You cannot assume the
tar.gz file is healthy but IMHO chances it is are quite good.
A very common root cause of the
"Error exit delayed from previous errors" is the fact a file has either its size changed while processed or has disappeared just before. Depending on what kind of files your archive contains, this can be a non issue. In any case,
tar is properly processing this kind of event and the archives created should be usable.
Next time you create your archive, I would suggest to forget the
v (verbose) option or redirect
stdout to a file. While it is useful for small archives containing a dozen files or so, it adds a useless noise to
tar output and you'll then have the error messages, if any, on screen and not lost in the terminal emulator scrollback.
tar czvf large.tar.gz someDirectory >/tmp/large.tar.list
Of course, there is no 100% guarantee your
tar.gz file is healthy. The only way to know it would be to extract it somewhere and see if no error show up. Even if it is the case, there is still the possibility some files weren't saved because of access rights issues, or more odd ones like file names / path names too long or invalid, corrupt file systems, corrupt transmission, etc ...