Shirt Pocket Discussions  
    Home netTunes launchTunes SuperDuper! Buy Now Support Discussions About Shirt Pocket    

Go Back   Shirt Pocket Discussions > SuperDuper! > General

Thread Tools Rate Thread Display Modes
Old 10-12-2004, 02:12 PM
Phil Phil is offline
Registered User
Join Date: Oct 2004
Posts: 3
Sparse Disk Image track record?

I've purchased SuperDuper for personal use and it looks very promising.

Additionally I support several digital photographers that are looking for a backup solution. They tend to need "versioning" less than authors or software developers for whom the file can change significantly day to day.

Given the cost, complexity, and declining robustness of Retrospect (which I've used for over a decade in businesses) I'm looking to develop an operating model for this group of friends using SuperDuper.

In general, I like the split of backuping up the System separately from User files. The System would be backed up to a bootable partition. As for User files, I like the idea of Smart Backups of the /User/xyz to a sparse disk image created with Disk Utility. (descibed in the FAQ The reason I prefer the sparse disk image, is that typically in would not be mounted, lessening potential confusion as which is the primary file and which is the backup. I realize that once it is mounted it looks just like a disk and confusion is possible. This group in particular varies quite widely in their awareness of the file system. Perhaps the distinction is too minor to matter.

Sorry for the long introduction. What I was wondering is does anyone have extensive experience with the sparse disk images? Are they reliable? Can they shrink, if the content is removed? When were they introduced to OS X and do they draw on a tested code base?

Any perspective would be greatly appreciated.

Reply With Quote
Old 10-12-2004, 02:52 PM
dnanian's Avatar
dnanian dnanian is offline
Join Date: Apr 2001
Location: Weston, MA
Posts: 14,923
Send a message via AIM to dnanian
Hi, Phil -- thanks for your post!

Sparse disk images have been around for quite some time, although they're rarely talked about. Apple themselves leveraged sparse images to implement FileVault, so it's been quite well tested.

I don't believe they shrink 'automatically', but since FileVault images will shrink, there's likely a command that could be used to compress them.

I believe, using a combination of saved settings and our upcoming AppleScript support (see your other question for more), you'll be able to quite easily develop a model that will unmount the sparse image and keep it 'out of mind'...
--Dave Nanian
Reply With Quote
Old 01-05-2005, 04:13 AM
SpinUp SpinUp is offline
Registered User
Join Date: Dec 2004
Posts: 2
Shrinking Sparse Images

I use a sparse image to back up and recently noticed that the file size has been growing far beyond the size of the data on the disk image. The sparse image had max size of 7 GB and contained only 4.95 GB of data, but the file size was 6.45 GB!

That seemed unreasonable, so I decided to look into shrinking it. Reading from here,

I found the hdiutil command "compact", which can be used in the terminal as follows:

hdiutil compact imagename.sparseimage
This removes the parts of the image file that aren't being used in the volume. The process ran for a couple of minutes, and the file size of the sparse image was subsequently reduced to a more reasonable 5.3 GB. Note that the above link is just the man page for hdiutil in Panther, and has this to say on the subject of reliability:

As of OS X 10.3, partially-updated SPARSE images are now properly handled such that they can be safely used for persistent storage. SPARSE images are not recommended for persistent storage on earlier versions of the operating system.
I was using sparse images for backup in Jaguar, when perhaps I shouldn't have been...
Reply With Quote
Old 01-05-2005, 01:45 PM
dnanian's Avatar
dnanian dnanian is offline
Join Date: Apr 2001
Location: Weston, MA
Posts: 14,923
Send a message via AIM to dnanian
Yes: sparse images are used for FileVault folders in Panther, and I know that they -- along with lots of other things -- took fixes for Panther (and later releases). But I believe sparse images work quite well as long as you don't get any internal corruption due to crashes and the like...

In any case, I absolutely recommend that people update to Panther. There are a lot of improvements in it, as there will be in Tiger. And we don't guarantee that any version past v2.0 will be Jaguar compatible: we just can't maintain backward compatibility forever -- it constrains new features too much, and makes our testing matrix far, far too difficult to execute.
--Dave Nanian
Reply With Quote

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
How do I update an image? dnanian Frequently Asked Questions 0 06-12-2004 10:05 AM

All times are GMT -4. The time now is 11:10 AM.

Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2024, vBulletin Solutions, Inc.