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"Hot-imaging" versus "Cold-imaging" (Read 28944 times)
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Re: "Hot-imaging" versus "Cold-imaging"
Reply #15 - Mar 28th, 2007 at 10:02pm
 
Rad wrote on Mar 28th, 2007 at 6:39pm:
I noticed in nbree's (Nigel) profile that he's a Ghost developer ("Principal Software Engineer"). Certainly that gives him huge credibility when it comes to discussing the intricacies of the prgm.

http://radified.com/cgi-bin/yabb2/YaBB.pl?action=viewprofile;username=nbree

http://nigel.bree.googlepages.com/

Welcome.

I can't help but wonder how long he's been developing Ghost. Back when I first started using Ghost (v5.1), it was hard (impossible) to find any help for it. I had to learn the hard way.


I have been following the symantec ghost forum (mostly used by enterprise users) and I find him very helpful in resolving issues /problems users encounter. In some instances he has been able to get hold of the developer colleague who worked on the original ghost engine to resolve problems. His help to ghost users has been very invaluable and as I have been been around some sticky and serious hardware and software problems with various software, I can easily realize the invaluable help he is rendering to the  Ghost users. I wish more of the software developers get active in the various software boards and forums and there is no substitute for developers' participation. Again thanks Nigel, we are all grateful for your time and help.

/me  Smiley
 
 
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Re: "Hot-imaging" versus "Cold-imaging"
Reply #16 - Mar 29th, 2007 at 6:13am
 
Rad wrote on Mar 28th, 2007 at 6:39pm:
Back when I first started using Ghost (v5.1), it was hard (impossible) to find any help for it. I had to learn the hard way.

Indeed, it would have been. You did a great many people a fine service by filling that gap with your excellent guide!

The way things worked with the division between Binary (who were totally focused on R&D) and the marketing side (BRI and the resellers who did consulting and support in various national markets) worked pretty well by the standards of the time, but these days the model for small ISVs to do it all using the web is a bit more well-trodden.

I don't take any credit for the cloning engine, by the way - that belongs entirely to Murray and the other notables at Sprite along with Nigel Pattinson and Andrew Haslam. I was brought in around 1997 by one of the serial entrepreneurs (Gray Treadwell, for whom I'd been a tame geek since the early 80's) who invested in Murray's business and helped grow the business up through to the sale to Symantec.

Anyhow, it turns out I have to correct myself; although IOCTL_VOLSNAP_FLUSH_AND_HOLD_WRITES was still undocumented as of late last year, it appears that it's recently become public, so now you can see the official word on the internal details for yourself. As with most of the design of NTFS itself, it's really just an implementation of concepts that have been pretty well understood for a long time in the database world  - indeed, the great and probably late Jim Gray who was at Microsoft Research for the last few years originally invented many of the key ideas and co-wrote the definitive book on the subject. That doesn't take anything away from the engineers at Microsoft who actually put VSS together, they did a good job with the internals of the implementation.
 
 
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Pleonasm
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Re: "Hot-imaging" versus "Cold-imaging"
Reply #17 - Apr 1st, 2007 at 10:48am
 
Nbree, I am confused.  The documentation for Norton Ghost 10 states "Norton Ghost is not integrated with Microsoft's Volume Shadow Copy service" (C:\Program Files\Norton Ghost\Shared\Readme.txt).

Information on the snapshot driver used by Norton Ghost 10 (developed by StorageCraft) is contained in this thread (see especially Reply #9).
 

ple • o • nasm n. “The use of more words than are required to express an idea”
 
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Re: "Hot-imaging" versus "Cold-imaging"
Reply #18 - Apr 2nd, 2007 at 7:44am
 
Quote:
The documentation for Norton Ghost 10 states "Norton Ghost is not integrated with Microsoft's Volume Shadow Copy service" (C:\Program Files\Norton Ghost\Shared\Readme.txt).

That could mean a number of things, and since I don't have access to their source I can't check, but I'd wager that it just means they use the volsnap.sys ioctl directly, rather than invoking the VSS system through the normal user-mode libraries (it's got an awfully overcomplicated set of COM APIs, and the version of VSS in Win2003 uses a different, incompatible API). Bypassing that simplifies things immensely, and given that very little of anything plugs into the VSS notification system (that's more useful for server code) it's reasonable to do that for WinXP.
 
 
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Re: "Hot-imaging" versus "Cold-imaging"
Reply #19 - Apr 3rd, 2007 at 8:23pm
 
Quote:
You did a great many people a fine service by filling that gap with your excellent guide!


It started with an email to a friend, which contained little more than:

Local > Partition > To Image


.. and grew from there.

Then I noticed I was typing the same email over & over, so I copied-n-pasted it into a web page, and posted it on a friend's site (pre-Radified days).

Once I got this site, I posted it here, and comments started coming in from all over the world, making suggestions.

The rest is history, and the guide continued to grow.

Thanks for your posts, which contain insights not available anywhere else.
 
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Re: "Hot-imaging" versus "Cold-imaging"
Reply #20 - Apr 4th, 2007 at 7:10am
 
Nbree, continuing the conversation from Reply #11, there has been considerable debate among forum members on whether or not "hot imaging" (e.g., Norton Ghost 10) is as reliable as "cold-imaging" (e.g., Norton Ghost 2003).  Your comments imply (and appear to confirm my own perspective) that both are equally reliable for Windows XP - and presumably for Windows Vista, too.  Of course, each image backup approach has some benefits and features that the other lacks - but specifically with respect to reliability, is there any reason to believe that one approach is any more or less reliable than the other?

Thank you.
 

ple • o • nasm n. “The use of more words than are required to express an idea”
 
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Re: "Hot-imaging" versus "Cold-imaging"
Reply #21 - Apr 6th, 2007 at 3:44am
 
Quote:
Of course, each image backup approach has some benefits and features that the other lacks - but specifically with respect to reliability, is there any reason to believe that one approach is any more or less reliable than the other?

In the abstract, no I don't think so, although it takes substantial engineering effort to make it so - especially, the cooperation of the filesystem to take on more transactional semantics - compared to offline work. The database world proved all this stuff works three decades ago.

Really, the only thing that's still missing in modern systems is that application programming doesn't support high concurrency and transactional semantics (well, except for functional languages, but despite also being technology proven decades ago they are still a hard sell).

Just to reiterate that hot-versus cold isn't either-or, there's a huge amount of value in having a tool ecosystem in which almost every piece can work either way, which is what we were pursuing in Ghost.  Imaging isn't just about "backup" or "deployment", as much as people like to put it into those categories - it's always a piece of a larger process, and it's nice to be able to give people the choices they need to have the imaging (and other) steps fit into whatever else they want to do.
 
 
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Re: "Hot-imaging" versus "Cold-imaging"
Reply #22 - Apr 6th, 2007 at 1:42pm
 
Nbree, as a Ghost developer and Principal Software Engineer at Symantec, your comments are especially appreciated on this forum.  Your observation that both “hot” and “cold” imaging approaches are equally reliable confirms what users of the former already expected, and may be a key tidbit of insight that allows others who have been hesitant to employ the technology to do so with enhanced confidence.

I am curious:  When you said, “…every piece can work either way, which is what we were pursuing in Ghost” (Reply #21), do you mean that Ghost Solution Suite will be adding (or transitioning to) a “hot imaging” approach?
 

ple • o • nasm n. “The use of more words than are required to express an idea”
 
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Re: "Hot-imaging" versus "Cold-imaging"
Reply #23 - Apr 6th, 2007 at 4:06pm
 
Pleonasm wrote on Apr 6th, 2007 at 1:42pm:
When you said, “…every piece can work either way, which is what we were pursuing in Ghost” (Reply #21), do you mean that Ghost Solution Suite will be adding (or transitioning to) a “hot imaging” approach?

I was speaking of our original plans, they got shelved by the PQ "acquisition". It remains technical good sense to add this, customers ask for it, and it's not exactly difficult to do since it's a standard API; however, nowadays it's entirely up to our masters in Orem whether this would ever happen in (real) Ghost. Your guess is as good as mine, basically.
 
 
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Re: "Hot-imaging" versus "Cold-imaging"
Reply #24 - Apr 8th, 2007 at 6:08pm
 
mr. nbree, being a developer of Ghost (one of the coolest programs in the history of software) .. makes you something of a legend. do you feel that way?

if your boot/system drive died .. and if your storage drive contained two back-up images .. one with the file extention *.gho (created by Ghost 2003) and another ending with *.v2i (or whatever file extention Ghost 9/10 produces) .. which would you consider more reliable? .. if you had to bet the farm on the restore working??
 
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Re: "Hot-imaging" versus "Cold-imaging"
Reply #25 - Apr 10th, 2007 at 6:35am
 
Rad wrote on Apr 8th, 2007 at 6:08pm:
mr. nbree, being a developer of Ghost (one of the coolest programs in the history of software) .. makes you something of a legend. do you feel that way?

It's worth repeating: I don't claim any special credit for the cloning engine. "Success has many fathers" in this case is literally true, along with a reasonable dose of good timing, good fortune, and a healthy amount of plain engineering grind. It's also the case that while you're in the middle of it, the negative feedback you get about your work is rather more direct, pointed, and available (e.g. customer complaints) than the positive feedback, which tends to be delayed and indirect (e.g. sales figures). Plus, there are plenty of obstacles that have to be overcome on the road which aren't very visible from outside.

Those aren't answers, of course. My honest answer is: no, not for a moment. A certain grim satisfaction is about the highest I can muster. Of course, that's not a very illuminating answer unless we were to dig into the why. I'd be happy to discuss that, since what drives us, our values and the yardsticks we use to measure ourselves as human beings are weighty and important topics (ones that you speak to directly in the Rad blog, when you talk about your son). We should perhaps do that outside this particular forum, though; I doubt the Norton Ghost 9 users want to wade through such philosophising.

Quote:
if your boot/system drive died .. and if your storage drive contained two back-up images .. one with the file extention *.gho (created by Ghost 2003) and another ending with *.v2i (or whatever file extention Ghost 9/10 produces) .. which would you consider more reliable? .. if you had to bet the farm on the restore working??

Given that I have the ability and access to fix any problem that could arise in Ghost it's not a question that I can answer in the abstract; I use Ghost, not just because I can but because it's right and proper for us to eat our own dogfood. Indeed, last time I did a boot drive migration at home (earlier last year) it was with the pre-GSS2 development code and helped find a bug.

The same is undoubtedly true of the PQ guys, and I have no doubt that they work every bit as diligently as we do. PQ was justly famous for Partition Magic, and deserved the reputation that brought them. Even as competitors we held their engineering skills in high regard; we and they took and still take different approaches to product design, which is a completely different matter entirely. I happen to feel similarly about most competing products, such as Acronis; I wouldn't criticise the engineering ability of their staff either.

Where all these products differ most is in other qualitative factors; some do quite different things, and so suit different purposes. For instance, PQ's totally sector-oriented approach accelerates incremental backups, while prior to the PQ acquisition it was clear we could extend AutoInstall to use VSS and the NTFS change-tracking facility in Win2k to create similar incremental file-oriented backups (which tend to contain more data and are thus slower to produce, but which would be applied with Ghost on top of any base image).

There's room in the world for all these, and no shortage of reasons to prefer one or another that aren't about technology. Really, most technological arguments about products are emphasising the wrong things: qualitative factors such as "flexibility" and "attractiveness" are harder to evaluate but end up mattering more where it matters most, in how users feel about their experience with a product. We're emotional beings, after all - which ties us back to your question about how I felt about being a developer.
 
 
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Re: "Hot-imaging" versus "Cold-imaging"
Reply #26 - Apr 10th, 2007 at 9:50am
 
Rad, the question you asked in Reply #24 – whether a .GHO image is more reliable than a .V2I recovery point – was answered in the negative by Nbree in Reply #21, correct?

As a practical matter, to the best of my knowledge, there have been no reported instances whatsoever on this forum or elsewhere of a PC failing to operate properly after a restore from a .V2I recovery point because the state of the machine as captured in the image was “inconsistent” (i.e., the transactional file system activity was improperly managed during the backup process).  That is the only potential point of weakness in a “hot image” approach, and as Nbree noted, the “database world proved all this stuff works three decades ago.”
 

ple • o • nasm n. “The use of more words than are required to express an idea”
 
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Re: "Hot-imaging" versus "Cold-imaging"
Reply #27 - Apr 10th, 2007 at 10:26am
 
Pleonasm wrote on Apr 10th, 2007 at 9:50am:
"... (i.e., the transactional file system activity was improperly managed during the backup process)..."

Then the question becomes: Is easier for a "ham-handed" user to precipitate improperly managed transactional file system activity when using either "hot-imaging" or "cold-imaging" Ghost products, or is it instead a "wash"?

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Re: "Hot-imaging" versus "Cold-imaging"
Reply #28 - Apr 10th, 2007 at 10:56am
 
El_Pescador, in theory, almost anything is possible.  I could certainly imagine situations where a user is doing “something exceedingly dumb” while a .V2I recovery point (or .GHO image, for that matter) is being created and thereby cause a problem.  However, even under those conditions, one would expect that the backup process would exit with an error message and a subsequent verify operation would also detect the problem.  (As we have cautioned users many times, it is foolish not to run a verify after a backup.)
 

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Re: "Hot-imaging" versus "Cold-imaging"
Reply #29 - Apr 10th, 2007 at 12:03pm
 
Quote:
[quote author=Rad link=1174840381/15#24 date=1176073688]It's also the case that while you're in the middle of it, the negative feedback you get about your work is rather more direct, pointed, and available (e.g. customer complaints) than the positive feedback, which tends to be delayed and indirect (e.g. sales figures). Plus, there are plenty of obstacles that have to be overcome on the road which aren't very visible from outside.


From an individual end user point of view, Ghost is a classic case of users finding it by word of mouth, not the traditional ad channels. I was told about it by another computer enthusiast when I was visiting a local computer store. And I guess it took some time before Ghost built up its following. From a end user point of view, it has been a godsend in having saved countless hours when something messed up the hardware or software. Our gratitude goes to the developers who fine tuned it to be what it is today.

/me  Smiley
 
 
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