To Ro wrote: > Here is another question: How does the creation of a tar.gz ball occur? Is > it
That is one of those questions like Bilbo's riddle. It is created by the commands that created it and there isn't any other way to know. Except that you said it was 400G and that means almost certainly it was created on the fly and not in place. > a) first compressing files and directories and then taring them > or If the file was 400G compressed then to have done that would have needed more space. If the compression was 10x (not uncommon) then it would have needed 4000G of space to hold the uncompressed image first and then enough additional space to create the compressed file. You would have needed, say, at least 5T of space in that case. Unlikely. And inefficient. (And it all depends upon the compression factor. Images are already compressed and generally do not compress more. My 10x number might be 1.2x overall. But text and source code and particularly data files tend to compress very well and my 10x number might be 100x then. It all depends upon the data.) > b) taring and then compressing? Normally people working with tar.gz files compress them on the fly. tar cf - DIRPATH | gzip > TARFILE.tar.gz Or they do the above combined all at one time using the 'z' option which does the same thing but is a nice typing saver aid. Internally tar will use popen() to create the pipe for you. tar czf TARFILE.tar.gz DIRPATH Since that runs as a pipe the output file is always compressed and disk space used is at a minimum. Also each process can get a different cpu in a multi-core cpu system. That is the most likely way that your 400G tar.gz file was created. However that is still not the only way and other possibilities exist so this can not be said with absolute certainty. > One experience I got: Never create big tar balls unless you have the > computer power to handle it. Especially if it is compressed. I have to say that when I saw that you had a 400G tar.gz I had a sharp intake of breath thinking about it. Good to hear that it was not ext3! Do what user green said and you may have good success recovering the file. Good luck! Bob
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