Backup Software Alternatives

SP/IFW will only inform you of the corruption when it reaches the corrupt bit, so your system partition will be left in a bad state. Perform a verify before starting the restore.

 

Defenestration,

It looks like you are the authority on this problem. The rest of us have no practical experience. Any information you can provide will be invaluable.

 

@Peter2150

I take back the poor software bit as other images softwares suffer the same problem hence the reason for verify. Thinking about it if the header of the image is intact which is where the info is kept about the image passed to the image program, it would see it as valid and wouldn't know other bits were corrupt further into the image. Image programs take a CRC (cyclic redundancy check) when the image is taken in real time so the data is saved to disk correctly. If a CRC could be taken for the whole image and stored then the image program would check before starting and know if the image was corrupt or not don't you think? Change 1 byte and the CRC is different. This would go an extra mile to ensure you don't put back a corrupt image or would taking a CRC of the whole image take as long as doing a verify.

 

A faulty image due to bad memory, was experienced by Defenestration and the impression was it would not restore.

But a partial restore was in fact possible.

So in such cases, a faulty partial restore is possible and my statement was not accurate.

Apart from this one, what is your experience with a corrupt SP image ?

If a corrupt image generally does restore, or even if there is doubt-then instant restore is worthless and dangerous, as regards testing and verifying is preferred.

So why are we recommending instant restore,instead of verifying,when the image may be corrupt?

Based on my general experiences, backups either restored or not-there were no grey areas,but admittedly this may not have been due to a corrupt image.

 

Pete,

getting back to the other issue:

If a corrupt image can be restored,dont you think we are wrong in recommending a test restore instead of a validate,as this could cause major problems.
Seems to me we definitely are,until we know more.

Surely merely extracting a zip file to test isnt sufficient,in that with Defenestrations example,the fault occured at a point where previous files may well have been OK.

Your test of betas-was that with SP or just generally?

Have you ever had a message like "SP cant restore" for example and how do we know this wasnt a corrupt file

 

Pete,

Dont think the real questions has been solved.

In the meantime suggest that what we previously recommended,ie a test restore not be carried out,as in the slim chance of a corrupt image happening,this would be then restored,with potentially disastrous results.

I agree that as far as I' m concerned also,my faith in SP is such that I will never even bother to verify.
But then comes the question-if we trust it so much,why bother with any sort of verify or test restore.

Think all of this came to light because of an isolated issue,but probably it would be confidence inspiring for some users to keep two images-1 known good fall back one and the current one-plus up to date backups of data.
If the current one is bad-then the fallback plus the data will make avert disaster.

Plus of course do a verify.

As far as I'm concerned as I said -wont even bother to verify!

Have asked for help from SP and will post if anything meaningful comes up

 

Hairy Coo,

Thanks for your efforts in throwing further light on making our backups safer. We don't have to think we don't trust your backup app when we verify as verify (validate) is also checking for hardware issues which may cause problems at restore time.

 

Looks like you are right about the verify,assuming it gives a true picture apart from hardware issues

 

I'll be interested to hear Nate's comments. He has already provided several scripts to allow us to verify our backups at regular intervals.

 

Yes,he's very helpful,but probably asleep.

Funny hours the Americans keep ,why cant they keep the same time as us,best time in the world

 

I don't really have any other information, other than what I've already provided. After seeing it can go wrong due to bad RAM though, when no errors were evident during normal usage of my PC (aside from image creation/verify/restore), Memtest86+ is my new friend

With hard drives being so cheap these days though, I would suggest purchasing another "spare" HD for testing purposes (eg. performing a restore after image creation and then booting from it).

 

nothing is 100 % reliable so you you have to live with that,sound images on failing ext. drives[diskrot],power outage,theft,lichtning,corrupt diskcontroller,mechanical failure etc and the list go on.
as said earlier to diminish the risk is to keep a string of images,and most importantly,to keep the very same image on different media,or on different external disks and if you are hyper paranoia,to chdsk these on a regular basis,or keep an eye on the SMART diagnostic utility provided with your drive.

that said SP,at least about the imaging part of it,keep me at ease,anything else,such as ext. media,disks etc.will remain uncertain or a gamble if you will.

 

Here is a reply from Admin.at ShadowProtect regarding this matter

Note some important points:

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