Tar Backups and Size Limits

[Janina Sajka]

Yes, Joeseph is right. It's a file size limit on FAT32. I ran into this
once myself some years back.

But, I would certainly not recommend ext2. I see no reason to give up
the journal. ext3 is very reliable and would give you more flexibility
and security as well.

Joseph C. Lininger writes:
> Hi,
> First, allow me to clear up a little bit of confusion regarding limits of 
> fat32. When you look at a filesystem, there are two major limits you will 
> run into. The first is an over all limit, meaning how large the entire 
> filesystem can be. The second limit is a bit more suttle. It is a limit on 
> the size of an individual file. The fat32 filesystem can support 
> filesystems up to 2 terabytes in total size. However, each individual file 
> in a fat32 filesystem may not be larger than 4gigabytes. Now, I will 
> address Steve's original question.
> 
> The tar program is designed for tapes, and all the -f option does is to 
> tell it to write the same contents to a file that it would write to the 
> tape. This means that when it hits the size limit you have specified with 
> -L it will simply start over with the next portion in the file. What you 
> have to do to get around this if you want to do it this way is to have a 
> script that runs in between each portion (see the -F option) which will 
> rename the file tar uses for its work to something else so that when tar 
> recreates it for the next part you don't lose the previous one. Tar does 
> not automatically provide this functionality. I can provide more details on 
> how such a script would work if desired.
> 
> You do have one other option. You could format the drive using ext2 or 
> ext3, and then use ext2fsd under Windows to read and write the filesystem. 
> The driver is not perfect, but it does work. This would overcome your size 
> limitation. This would also allow you to use the -j option to tar since you 
> would be using a single file, meaning the file would be much smaller since 
> you would be using compression.
> --
> Joseph C. Lininger
> jbahm at pcdesk.net
> Verification: 5eab38a77ac40416e075be8f50607ff7
> ----- Original Message ----- 
> From: "Steve Holmes" <steve at holmesgrown.com>
> To: <speakup at braille.uwo.ca>
> Sent: Sunday, November 07, 2004 1:24 AM
> Subject: Tar Backups and Size Limits
> 
> 
> >-----BEGIN PGP SIGNED MESSAGE-----
> >Hash: SHA1
> >
> >Hey, I'm trying to backup my linux system (home directories to a 200
> >GB external drive using tar.  It seems that there is an upper size
> >limit either due to the fat32 file system on this external drive or
> >tar.  I can't emagine tar having imposed any limits.  So I tried to
> >use -M multi-volume option and a -L limit of 4GB.  It got through the
> >first file seemingly ok and it put up the prompt to start the next
> >file.  Well, I figured tar would just go ahead and create the next
> >file with a different suffix or something.  Well, it appears that it
> >did not.  When I looked in another console I saw that the size of the
> >second archive started over as I would expect but it is actually the
> >original file.  In other words, I think the back procedure is
> >overlaying the first file.  The tar command I used is:
> >tar -cvf archive.tar -M -L 4000000 FILES...
> >
> >I figured later I would do incremental backups against this tar file.
> >Am I missing something? If I reformatted my external drive as ext3 or
> >something, I could probably have done all this without size limits but
> >I also intend to use this same drive to backup my winblows boxes as
> >well.  This is a 200 GB drive with a pre configured VFAT single
> >partition.
> >
> >Any ideas out there? Thanks.
> >
> >- -- 
> >HolmesGrown Solutions
> >The best solutions for the best price!
> >http://ld.net/?holmesgrown
> >-----BEGIN PGP SIGNATURE-----
> >Version: GnuPG v1.2.4 (GNU/Linux)
> >
> >iD8DBQFBjdulWSjv55S0LfERAjvcAJ4nP7C/cVtMo6iLhoHqCg94skviVgCeMdQF
> >2kuZ0rrTJ+K7r4TbTsWkAh8=
> >=nOgl
> >-----END PGP SIGNATURE-----
> >
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-- 
	
				Janina Sajka, Chair
				Accessibility Workgroup
				Free Standards Group (FSG)

janina at freestandards.org	Phone: +1 202.494.7040