What is a "sparse disk image"?

dschwartzer

I am struggling to get a backup onto an external Ethernet Hard Drive I have attached to my network. I am told by tech support for the back-up software (SilverKeeper) that the problem may lie in the fact that I am trying to use a "sparse disk image" on the network drive.



The drive is currently formatted in FAT32 because I have 2 Macs and 1 PC using the drive. The suggestion is to reformat it using HFS+ or EXT3 but if I use HFS+ I don't think the PC will be able to write to or read from the drive. I can't partiction the drive because I want all three machines to share a common music library for iTunes.



Can someone tell me what a "sparse drive image" is? Will reformatting the drive to HFS+ eliminate the problem (assuming I can overcome the PC issue?



Thanks,





David

nguyenhm16

A sparse disk image is one that is normally X bytes but only takes the number of bytes actually in use. In other words, if you create a 40GB sparse disk image, it will report that 40GB free (give or take some overhead, of course), but the disk image file will not take 40GB until you have 40GB of data on it. Dunno why the underlying filesystem would care, since the disk image is just a file that grows or shrinks.

jwink3101

Also, (and this is very important), a sparsedisk image will not shrink on its own. So if you create a 20 gig disk, put 15gigs in, you will have five left. If you take out another 5, you will still only have five. The way to shrink them is to either do this: http://www.macosxhints.com/article.p...ry=sparseimage or create an apple script to do it with this: http://www.macosxhints.com/article.p...41207153823222



I use sparsedisk images all the time becuase you can encrypt them. I use them to keep a file contaning bank account and credit card numbers. I also use them to keeps other files from friends who are always trying to find them and embarrass me. (my journal or course...or is it).

mr. h

Your problem could be that you're using FAT32, which doesn't like files bigger than 4 gigs. Try NTFS instead if you're using Windows NT, Windows 2000 or higher. PCs can handle HFS+ discs if you use MacDrive.