Welcome, Guest. Please Login
 
  HomeHelpSearchLogin FAQ Radified Ghost.Classic Ghost.New Bootable CD Blog  
 
Pages: 1 2 
Send Topic Print
Reliability of incremental images with Ghost 9/10 (Read 7735 times)
Rad
Radministrator
*****
Offline


Sufferin' succotash

Posts: 4090
Newport Beach, California


Back to top
Reliability of incremental images with Ghost 9/10
Jan 31st, 2006 at 1:35pm
 
Can someone who has experience with Ghost 9/10 characterize the
reliability of incremental images
(imaging)?

I thought I read about some problems with that feature, but may be mistaken.

Seems it adds another place where something can go wrong.

Would you say a
baseline image
(correct terminology?) is more reliable than an incrementally-updated image?

Is there a limit to the number of times an image can be updated incrementally?

What is the time difference between a baseline and an incremental .. in general?

Am I being paranoid?

http://www.randomhouse.com/doubleday/currency/catalog/display.pperl?isbn=9780385...
 
WWW  
IP Logged
 

Pleonasm
Guest




Back to top
Re: Reliability of incremental images with Ghost 9
Reply #1 - Jan 31st, 2006 at 3:02pm
 
Rad, you are correct:  in a Symantec document it is stated that a possible cause for a restore failure may be a restore point that is either spanned (i.e., one image split into two or more files) or is incremental.  Unfortunately, I can’t find the citation to this document at the moment, but I know that the caution exists.

Additionally, “Severe fragmentation can prevent Norton Ghost from getting a ‘clear’ recovery point of the drive” which may cause a restore problem (see error E0BB0004 in the Norton Ghost 10.0 User’s Guide, page 137).

To maximize reliability, it appears that a user should:
  • Write a recovery point (image) to a single rather than a split file.
  • Avoid the use of incremental recovery points.
  • Defragment the hard disk drive before creating a recovery point.
What is unknown is the extent to which these actions actually impact reliability.  Is it an extremely rare occurrence that impacts only some unique PC configurations – or, is it more frequent and ubiquitous?

As is the case with most decisions, there is a cost/benefit tradeoff.  Incremental recovery points may be extremely convenient, and that high benefit may be more than offset by a small increase in risk.  It is a personal decision that each PC will need to make.
 
 
IP Logged
 
John.
Übermensch
*****
Offline



Posts: 2072


Back to top
Re: Reliability of incremental images with Ghost 9
Reply #2 - Jan 31st, 2006 at 3:57pm
 
Rad, for my 2 cents worth here, I would first say that in general I agree with Pleo.
Theoretically
it *should* always be better/safer to have a single complete unsplit full base Ghost 10 backup file stored on an external device (with the Ghost 10 option selected to verify the image after the backup).

I also like to delete temp and temp internet files, defrag my C: drive, all before taking the backup image.  Just to make the backup smaller, cleaner.  I also (every week or so) run chkdsk c: /f to make sure my c: is in order.  All these are just precautions for wanting/needing a "clean" backup.

Quote:
Is there a limit to the number of times an image can be updated incrementally?

I don't think there is inherently anything wrong with incrementals or incremental recovery points.  Since you can't really control *when* Ghost will decide to take a full/basline backup even when you requested an incremental, I don't think it is a worry.  I can't imagine a scenario where you would end up with one baseline image on February 1st, and 27 more incrementals for the rest of the month.  Probably even a week would be stretching it.

But, just to be realistic and theoretical again, remember tape backups?  Full backups were often taken on weekends, and incrementals (or differentials) taken during the week.  To restore, you had to first restore the full backup; then restore one of more incrementals.

Same logic applies to database backups:  Usually the full backup has to be augmented with applying the transaction log kept since the full backup.  If one of the transaction logs (tape incrementals or Ghost incrementals or anybrand-software incrementals) is corrupt, you have to revent back to the full backup.

So, theoretically, 7 full/baseline backups are safer than 1 full backup and 6 incrementals.
 But the convenience of incrementals and space (or tape or time) considerations usually means there is a slight compromise level taken, with some small sacrifice in *theoretical* reliability.

Quote:
Am I being paranoid?

No, just cautious.

All this is just my 2 cents worth again.  I know from reading here that Brian has some good experiences with incrementals, so he can give his own 3 cents worth.   Smiley 
All opinions from anyone welcome!


I bet we all know friends, peers, companies, customers that have NO backup at all, or *think* they have a back but have never tested it, only to find out it doesn't work.

So your question and comments (and this board in general) is dear to my heart, because backup is so so so so important, yet we all are the ones that get called when *they* didn't even think of the consequences, much less do anything about it.
 

Ghost4me  Ghost 9, 10, 12, 14, 15.  Windows XP, Vista, Windows 7
 
IP Logged
 
Pleonasm
Guest




Back to top
Re: Reliability of incremental images with Ghost 9
Reply #3 - Jan 31st, 2006 at 6:20pm
 
Maybe there is a simple reason why an independent recovery point followed by, say, ten incremental recovery points is potentially more error prone.  Logically, it may be just a consequence of two conditions.
  • If the probability of any one entry in the NTFS Master File Table becoming corrupted is p, then the probability of the independent recovery point plus ten incremental recovery points is equal to p x (1+10), in this example.
  • If the probability of any one disk block becoming corrupted is p, then as the total size of the backup image increases, so too does the likelihood of an error – i.e., p(independent recovery point) < p(independent recovery point + ten incremental recovery points) because the size the former is less than that of the latter.
In other words, this issue may have nothing to do with the Ghost 9/Ghost 10 application per se; rather, it may be simply be correlated with the characteristics of the NTFS Master File Table and the media.

As I noted earlier, as p approaches zero, the issue rapidly becomes one of "theory" versus "practice."
 
 
IP Logged
 
Brian
Demigod
******
Offline



Posts: 6304
NSW, Australia


Back to top
Re: Reliability of incremental images with Ghost 9
Reply #4 - Jan 31st, 2006 at 6:23pm
 
Good questions Rad.

I haven’t been able to find objective data on incremental reliability.

I like incrementals as they are small and you can have many more backups on your computer. I do a baseline backup weekly and incrementals daily and I keep 20 to 30 images. Why not, I have the space. But I don’t have the space for 20 to 30 baseline images. I have a low threshold for restoring an image. If something is wrong and I can’t fix it easily then I restore to the previous day. Even with this many backups I don’t think I’ve used one more than a week old so it's really overkill.


I do baseline images weekly and incremental images daily. Mostly this works. Only occasionally a baseline image is done instead of an incremental. If there is a power blackout the next image is always a baseline.


On one occasion I couldn’t use a particular incremental but I can’t recall the error. I restored to the day before. Even if none of the incrementals worked, I still have several baseline images. I’m lazy. I don’t want to restore a three month old image and then have to redo three months of tweaks.

Time. A few minutes for a baseline and 20 to 30 seconds for an incremental. Imaging time is irrelevant as imaging is done automatically and you don't notice it happening. I only look at my images when I manually delete the oldest 7.

Everyone has a different approach to backups. One of my friends "backs up" by reinstalling Windows. I don't want to do that.

Rad, the link doesn’t work.
 
 
IP Logged
 
John.
Übermensch
*****
Offline



Posts: 2072


Back to top
Re: Reliability of incremental images with Ghost 9
Reply #5 - Jan 31st, 2006 at 6:51pm
 
Quote:
remember tape backups?

I have some old QIC-80 tape cartridges which hold a whopping 120MB each if anyone is interested. . . I'll even through in a couple diskettes for free too.  Smiley

I think I could get everything on one tape at the time.
 

Ghost4me  Ghost 9, 10, 12, 14, 15.  Windows XP, Vista, Windows 7
 
IP Logged
 

Rad
Radministrator
*****
Offline


Sufferin' succotash

Posts: 4090
Newport Beach, California


Back to top
Re: Reliability of incremental images with Ghost 9
Reply #6 - Feb 1st, 2006 at 1:33am
 
Thx for the excellent feedback. Read the responses twice and fixed the link.

Well, yeah .. there's the US$64K question:

What is unknown is the extent to which these actions actually impact reliability.  Is it an extremely rare occurrence that impacts only some unique PC configurations – or, is it more frequent and ubiquitous?


RE: "
Since you can't really control *when* Ghost will decide to take a full/basline backup even when you requested an incremental
"

How does that work? If Ghost sees there *much* has changed between baseline & requested incremental, it will *automatically* generate another baseline? Is there a number associate with this? A percentage? This seems to add an element of safety.

RE: "
because backup is so so so so important
".

Couldn't agree more.

RE:"
If something is wrong and I can’t fix it easily then I restore to the previous day
."

How does the incremental restore work? If you baseline on Sunday, and incremental each weekday, and have problem on Friday .. do you 1st restore baseline, then each incremental: Monday's, then Tuesday's ..etc.

Or just baseline + Thursday's.

Or just Thursday's incremental, and Ghost knows how to do the rest?
 
WWW  
IP Logged
 
Brian
Demigod
******
Offline



Posts: 6304
NSW, Australia


Back to top
Re: Reliability of incremental images with Ghost 9
Reply #7 - Feb 1st, 2006 at 1:44am
 
Rad wrote on Feb 1st, 2006 at 1:33am:
What is unknown is the extent to which these actions actually impact reliability.  Is it an extremely rare occurrence that impacts only some unique PC configurations – or, is it more frequent and ubiquitous?




You should add "Or not at all". Where is the data for any of these thoughts?
 
 
IP Logged
 
Rad
Radministrator
*****
Offline


Sufferin' succotash

Posts: 4090
Newport Beach, California


Back to top
Re: Reliability of incremental images with Ghost 9
Reply #8 - Feb 1st, 2006 at 1:51am
 
Well, I guess baseline on Sunday + daily incremental is better than just baseline on Sunday. The worst that can happen is you can't restore daily incremental, which is the same as if you never performed the daily incremental. Right?

RE: "
One of my friends "backs up" by reinstalling Windows
"

Uh, that's not a back-up. That's what you do when you don't have one.
 
WWW  
IP Logged
 
Brian
Demigod
******
Offline



Posts: 6304
NSW, Australia


Back to top
Re: Reliability of incremental images with Ghost 9
Reply #9 - Feb 1st, 2006 at 2:12am
 
All I'm saying is that nobody knows the reliability answers. At least publically.
 
 
IP Logged
 
NightOwl-
Übermensch
*****
Offline


"I tought I saw a puddy
tat...."

Posts: 2094
Olympia, WA--Puget Sound-USA


Back to top
Re: Reliability of incremental images with Ghost 9
Reply #10 - Feb 1st, 2006 at 2:32am
 
Rad

Quote:
RE: "One of my friends "backs up" by reinstalling Windows"

Uh, that's not a back-up. That's what you do when you don't have one.

Aaahhh--been there, done that--now I use Ghost  Wink !
 

No question is stupid...but, possibly the answers are Wink !&&
 
IP Logged
 

John.
Übermensch
*****
Offline



Posts: 2072


Back to top
Re: Reliability of incremental images with Ghost 9
Reply #11 - Feb 1st, 2006 at 2:44am
 
Quote:
RE:"If something is wrong and I can’t fix it easily then I restore to the previous day."

How does the incremental restore work? If you baseline on Sunday, and incremental each weekday, and have problem on Friday .. do you 1st restore baseline, then each incremental: Monday's, then Tuesday's ..etc.

Or just baseline + Thursday's. 

Or just Thursday's incremental, and Ghost knows how to do the rest?


I've never had to do a full restore using incrementals with Ghost 10, but my understanding is:

Ghost 10 calls each backup a Recovery Point.  So you basically get the listing from Ghost's catalog (nice screen actually) and choose which Recovery Point (which is a date and time for a specific backup drive).  Then Ghost takes care of it.

Maybe someone else who has actually done this can confirm.
 

Ghost4me  Ghost 9, 10, 12, 14, 15.  Windows XP, Vista, Windows 7
 
IP Logged
 
Brian
Demigod
******
Offline



Posts: 6304
NSW, Australia


Back to top
Re: Reliability of incremental images with Ghost 9
Reply #12 - Feb 1st, 2006 at 2:53am
 
Ghost 9 and 10 work the same for restoring to Thursday. Just choose the Thursday recovery point (incremental image) and off it goes (from the RE for the OS). You don't need to consider the baseline image but naturally all recovery points need to be in the same folder so Ghost can use the Baseline and all intervening incremental images.
 
 
IP Logged
 
John.
Übermensch
*****
Offline



Posts: 2072


Back to top
Re: Reliability of incremental images with Ghost 9
Reply #13 - Feb 1st, 2006 at 7:40am
 

Here's a sample screenshot of my Ghost 10 Recovery Points.  Note that I can choose which date I want to select for each partition that is backed up.  Once I select the Recovery Point, then I can use the Ghost Recovery Browser to select specific folders.  You can also mount the recovery point as a drive letter, which can be handy.  


...

 

Ghost4me  Ghost 9, 10, 12, 14, 15.  Windows XP, Vista, Windows 7
 
IP Logged
 
Pleonasm
Guest




Back to top
Re: Reliability of incremental images with Ghost 9
Reply #14 - Feb 1st, 2006 at 11:19am
 
Rad, returning to your original question, I think it is noteworthy that there has not been a single instance of a user of Ghost 9/Ghost 10 reporting a restore failure on this forum based upon incremental recovery points, to the best of my recollection.

It certainly seems that the vast majority (but not all) of the ‘problems’ that appear on this forum for all versions of Ghost (2003/9/10) are related to hardware compatibility issues (e.g., RAID, USB).
 
 
IP Logged
 
Pages: 1 2 
Send Topic Print