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Is it possible to take a full copy of the system (C:) drive in Windows 7 to another disk, whilst running the OS.

The intention is, to keep 2 drives in the system (a main drive and a backup drive) and occasionally "mirror" the main drive to the backup drive. Then, in the event of a complete drive failure, to be able to replace the failed drive with the backup drive, boot and go. No restore process, no rebuilding raid arrays, no use of "dynamic disks".

I assume, to be able to copy the in-use system files, then this would have to utilise something like VSS.

Does anyone know if a) this is even possible and b) which backup tools can be used to achieve a full copy. Of course, it would be of most use if subsequent "mirrors" are made differentially.

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4 Answers

up vote 2 down vote accepted

why not use RAID-1? that's exactly the kind of thing it's for. in fact, raid-1 IS "mirroring".

NOTE: RAID is NOT a substitute for backups. you'll still need to backup your data regularly, to tape or something....but a RAID array will both reduce the likelihood you'll need to run a full restore (always a PITA), and keep the system up and running on the single remaining disk while you swap the dead drive ASAP.

btw, for added redundancy you can add a third (or fourth etc) drive to the RAID-1. you'll still have the same storage capacity as just one drive, but all 3 (or 4 etc) drives would have to die simultaneously for your system to be down.

or, with 3+ drives you could use RAID-5 - but ONLY if you have a good hardware raid card with non-volatile cache. this emphatically does not include the fake-raid rubbish commonly found on motherboards - that's really just software raid with a special driver.

with R5 you get (n-1) storage capacity where n=the number of disks in the array....but write speed is abysmal unless you have a good cache. and it needs to be non-volatile to avoid corruption in case of power failure or crash.

the catch with raid-5 is that if you have 3 drives in the array, if one disk dies you're OK...but if two disks die, you lose everything. again, you can increase the redundancy by adding hot-spares, similar to adding extra disks to RAID-1.

or if you have 4 drives or more, you could use RAID-6. glossing over the details, it's pretty similar to raid-5 except that you have (n-2) capacity, and you can afford to lose two drives in the array before you lose the lot.

personally, i like and use RAID-1 the most. it saves your data without imposing a huge performance penalty. i'll use it in preference to R5/R6 unless disk space is at least as important as redundancy.

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It's largely an academic question, really (but it is something i would like to try and implement, if at all possible). I keep backups on-site on a large raid 5 array and then archive them offsite. This is more of a question as to whether it is possible to have a "plugin-and-go" spare boot drive that doesn't need to spend time re-building, restoring, or suffer from raid's somewhat fussy fragilities. No hardware needs to be purchased to get back up (a raid-1 would need its failed drive replacing before becoming operational). I value your input, but this question is specifically about not-raid. –  Cheekysoft May 3 '11 at 8:42
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actually, a raid-1 one would NOT need its failed drive replaced before it became operational. it can run just fine with only one drive remaining - that's the whole point of R1. otherwise implementing R1 would increase the risk of filesystem failure rather than reduce it. you asked about mirroring, and RAID-1 is the answer. on a unix or linux box, you could make do with rsyncing (or cp or even tar cf - | tar xf -) all the files to another drive, but windows just won't boot when you mirror at the file level like that....it's persnickety about where exactly on the disk its system files are. –  cas May 5 '11 at 9:37
    
I'm a victim of my own misunderstanding again. Thanks for setting me straight. –  Cheekysoft Dec 19 '11 at 13:37
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You'll have to try this, as I haven't. The built-in Windows VHD backup should do what you want, as 7 can boot from VHD.

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The problem with your approach is you will only have a crash-consistent copy of the disk if you pull it while it is hot. Usually crash consistent will boot ok, but no promises.

How about two spare mirror disks, shut the pc down periodically and swap the mirrors. The one you pull will be good should you need it.

Another alternative is to run win 7 as a virtual and run from a snapshot. Every so often, shut down, commit the snapshot and restart under a new snapshot. Any problems, drop the snapshot, boot from the base.

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