Welcome to the MacNN Forums.

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

You are here: MacNN Forums > Software - Troubleshooting and Discussion > macOS > Time Machine vs. System Restore vs. Volume Shadow Copy

Time Machine vs. System Restore vs. Volume Shadow Copy
Thread Tools
kcmac
Mac Elite
Join Date: Jan 2001
Location: Kansas City, Mo
Status: Offline
Reply With Quote
Aug 7, 2006, 10:25 PM
 
Ye of greater knowledge than I, please enlighten me.

It seems TM can restore specific files from any application. SR restores a snapshot of everything at a point in time you select.

Volume Shadow Copy, I am totally clueless but it looks like a business server solution.
     
The Mick
Senior User
Join Date: Dec 2002
Location: Rocky Mountain High in Colorado
Status: Offline
Reply With Quote
Aug 7, 2006, 10:53 PM
 
Originally Posted by kcmac
Ye of greater knowledge than I, please enlighten me.

It seems TM can restore specific files from any application. SR restores a snapshot of everything at a point in time you select.

Volume Shadow Copy, I am totally clueless but it looks like a business server solution.
System Restore in Windows XP does not keep any of the users' files but only stores files related to the OS. In case of a corruption you can theoretically "restore" the OS to a previous state. This assumes that the user either manually ran a snapshot of the system, or the OS automatically created one recent enough to be valid. Windows XP often runs automatic snapshots at the beginning of an application install for example.

Pesonally, as a Windows System Engineer, in the almost 5 years since Windows XP was released I have never once resolved a problem on a machine by using this feature.

Volume Shadow Copy is two-fold. There is a service that can be initiated by either Windows or third-party programs (e.g. Veritas BackupExec) to perform live state backups of critical system files, such as the Microsoft Active Directory database. There is no user interface for this service.

The other half of Volume Shadow Copy is for taking point-in-time snapshots of the entire contents of volumes. Think taking a snapshot of all the files on the D: drive of a server where all your company data resides. This feature is only available on Windows Server 2003. Windows XP Service Pack 2 included the client file restore utility, which beforehand had to be installed seperately. The idea is to take periodic snapshots of your data files on the servers so that if a bonehead user deletes or corrupts a file, they can use the utility to recover it from the last successful snapshot.

In real life, I have always disabled the Volume Shadow Copy for folders feature because the performance impact while it runs the shadow copy has brought entire offices to a halt.

I'm not going to call an ambulance this time because then you won't learn anything.
     
kcmac  (op)
Mac Elite
Join Date: Jan 2001
Location: Kansas City, Mo
Status: Offline
Reply With Quote
Aug 7, 2006, 11:18 PM
 
Thanks for the info.

So neither SR or VSC allows for specific file restore like Time Machine?

TM just looks so exciting.

I am interested to see how large these backups are, what kind of options you have to set a time limit (how far back in the past you want to go) etc.

The external hard drive makers must be licking their chops.
     
winterlandia
Forum Regular
Join Date: May 2001
Location: Bill Gates' Basement
Status: Offline
Reply With Quote
Aug 7, 2006, 11:24 PM
 
Volume Shadow Copy is almost exactly like TM as far as I can tell from today's demo. We use it constantly at my office to do quick restores for folks. It doesn't look snazzy like TM and is just an explorer window but it looks to be doing the same thing. You basically do a properties on the file/folder pick the 'previous versions tab' and you have (up to) 64 'snapshots' in time (we have ours set to snap twice a day during business hours and then let backup take care of the offsite tape backup at night). It actually works amazingly well. The snaps are very intensive on the server but since we have pretty high end HP stuff it really isn't noticable to any of the users.

I should clarify that MS's VSC looks a lot like TM but it is unlikely that it works that way. For example if you have your shadow copy volume as a different drive and the main drive fails you are sol. The shadow copy location only captures 'byte level changes of the original' so if the original is gone your sc is not worth anything. I'm guessing TM works this way but I'm not sure. There are different products from MS and Veritas that actually copy all the data and the shadows over to a separate volume but it's mainly for servers.

Also, while VSC is a service in XP, it doesn't seem to do anything there. It seems to only work in Server 2003. Looks like it is on the list for Vista though.

The only downside is that it wastes a lot of space and keeps a lot of data you may actually WANT deleted permanently hanging around.
( Last edited by winterlandia; Aug 7, 2006 at 11:31 PM. )
     
gperks
Dedicated MacNNer
Join Date: Oct 2003
Location: Round Rock, TX
Status: Offline
Reply With Quote
Aug 8, 2006, 12:32 AM
 
One thing I noticed in the Address Book demo... the search is still active in Time Machine. TM went searching back for a change in the current Spotlight context.

It's like Spotlight indexes back in time too.
     
besson3c
Clinically Insane
Join Date: Mar 2001
Location: yes
Status: Offline
Reply With Quote
Aug 8, 2006, 12:45 AM
 
I want to know if Apple had to change their file system to accommodate this. Other implementations (e.g. OpenVMS) exist within the file system. I suppose Apple could have also written versions to a giant database, perhaps similar to a Spotlight index.

I'm also hoping that Apple figured out a way to minimize disk space by developing some sort of system that only tracks changes, and doesn't keep hard copies of the files. Keeping hard copies of files already exists now in several solutions, perhaps the most popular being something like RCS, CVS, or Subversion.

Here's a list of version control products:

http://linas.org/linux/cmvc.html

Might be a little out-of-date, since I don't see anything about Subversion (which many developers are replacing CVS with).
     
demograph68
Professional Poster
Join Date: Jul 2003
Status: Offline
Reply With Quote
Aug 8, 2006, 02:53 AM
 
     
analogika
Posting Junkie
Join Date: Feb 2005
Location: 888500128
Status: Offline
Reply With Quote
Aug 8, 2006, 03:28 AM
 
Originally Posted by winterlandia
The shadow copy location only captures 'byte level changes of the original' so if the original is gone your sc is not worth anything. I'm guessing TM works this way but I'm not sure. There are different products from MS and Veritas that actually copy all the data and the shadows over to a separate volume but it's mainly for servers.
Jobs explicitly said that if your main hard drive dies, you just plunk in a new one, restore, and keep working.
     
mitchell_pgh
Posting Junkie
Join Date: Feb 2000
Location: Washington, DC
Status: Offline
Reply With Quote
Aug 8, 2006, 04:38 PM
 
Time Machine makes my head hurt.

I guess it would keep a up to date copy of the file... and a database of edits to the file... so if you go "back in time" it simply continues applying edits in reverse?

My question: How much space is this going to take. Say I have a 250 GB drive... how large of a drive will be needed to implement TM?

P.S. I'm VERY happy to see Apple implement this. I'll planning on using it from Leopard release on.
     
bilbo--baggins
Fresh-Faced Recruit
Join Date: Jan 2006
Status: Offline
Reply With Quote
Aug 8, 2006, 05:15 PM
 
Ok, in the event of hard drive failure this sounds great, but from my experience this is uncommon (in 16 years I've never had one fail - oops, what have I said...?).

However, file corruption for me seems to be a much more common scenario. Preference files getting screwed up, files going missing (when it's impossible that someone else could have interfered), excel spreadsheets becoming corrupt, etc etc. I wonder how robust Time Machine will be at overcoming problems like that. If it's 100% reliable, then this is one of Apple's greatest innovations ever. Probably even better than spotlight - which for me has made an incredible difference to my life (sounds like I'm being sarcastic, but honestly Spotlight deserves far more recognition that it currently gets).

I wonder whether it is necessary to keep a backup of the backup with Time Machine. I mean, do you have a 250GB drive as you main drive, with just current versions of everything, and a 500GB backup drive with both current and historic versions? If your backup drive fails, have you lost all the historic versions? It will be interesting to see how Backup (Apple's software with .Mac) fits into this. As well as having automated backups to a second hard drive, I currently make occasional backups to heaps of DVD's! If Time Machine is 100% corruption proof, then perhaps this won't be necessary any more.
     
besson3c
Clinically Insane
Join Date: Mar 2001
Location: yes
Status: Offline
Reply With Quote
Aug 8, 2006, 05:19 PM
 
Originally Posted by mitchell_pgh
Time Machine makes my head hurt.

I guess it would keep a up to date copy of the file... and a database of edits to the file... so if you go "back in time" it simply continues applying edits in reverse?

My question: How much space is this going to take. Say I have a 250 GB drive... how large of a drive will be needed to implement TM?

P.S. I'm VERY happy to see Apple implement this. I'll planning on using it from Leopard release on.


I think to reverse changes to binary data, you would need to do some stuff at the file system level. I''m curious to see how Apple implemented this.


Like I said before, it would kind of suck if TM just kept multiple versions of hard copies of the (binary) file, as that would drain HD space pretty quickly.
     
   
Thread Tools
 
Forum Links
Forum 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
Top
Privacy Policy
All times are GMT -4. The time now is 01:19 AM.
All contents of these forums © 1995-2017 MacNN. All rights reserved.
Branding + Design: www.gesamtbild.com
vBulletin v.3.8.8 © 2000-2017, Jelsoft Enterprises Ltd.,