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Some background:

I have been helping my uncle, a photographer, maintain a system of storage for all his work (Terrabytes of images!).

We do this by using two external hard drives for his data storage.

One of them we call the "Work Horse" drive, which he uses for working on files in Photoshop etc. thoughout the day. The other, called "Archive", receives any changes (using SyncToy) to the Work Horse on a daily basis.

When the external drives start to get full, the pair of drives are eventually disconnected from the system, replaced by a new pair of drives. The full work horse is then stored on-site , the Archive at a family member's house.

We have used this approach for the past few years - and I am now starting to think about 'refreshing' some of the older drives to prevent the effects of 'bit flux' or 'bit rot'.

The Question:

Is using the bad sector check included in Windows 7's chkdsk sufficient for revitalising every bit of data on these drives? If not, do any of you have a better solution?

Please bear in mind, I am aware using Tape backups would probably be best (as they are purpose built for archiving) but these are not an economically viable option for my uncle at present.

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Remember that a complete verification (read+write) of every single bit on massive HDDs will probably take hours, especially if connected via USB (even USB 3.0). That said, if you're looking for a Windows utility check out HDDScan and HDD Tune among others. –  Karan Dec 4 '12 at 21:42
@Karan thanks, am aware it is a slow process, but could just be left to run over night. The utilities you provided are fine for checking SMART attributes and benchmarking, but not to do a bit-by-bit read or read/write... unless I'm missing something? –  killercowuk Dec 6 '12 at 12:01
As per the screenshots on the site HDDScan seems to have a surface test feature that has read, erase and verify options, but maybe I misunderstood what they do. –  Karan Dec 6 '12 at 14:32
@Karan, I must apologise you're spot on. Tired eyes this morning! I'll give these a go +1 for your first comment. Would be good to know if a chkdsk bad block check does something similar. –  killercowuk Dec 6 '12 at 15:47
I don't think chkdsk does a full read+write+read+compare, but I could be wrong. –  Karan Dec 6 '12 at 16:24

2 Answers 2

Simple yet effective method to refresh data is to use badblocks, it's a linux utility that can check for bad blocks. It has a feature which allows non-destructive read-write test, which rewrites data on hdd by testing pattern, checks that pattern and write back original data.

Almost every linux distribution contains this utility as a part of e2fsprogs package. You can use for example live cd/usb SystemRescueCD

It is also part of cygwin packages, so you may be able to use it under Windows.

I'm not sure about this, but I think that chkdsk is performing only read test.

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Thanks week! I am a linux user myself, however admit I've never used/seen badblocks before. I'll have a look into it, however I am aware my uncle is not such a proficient PC user. Ideally would be great for him to have a set of instructions I can prepare that uses a native Windows program or app. –  killercowuk Dec 3 '12 at 13:07

Check out ExactFile. It's freeware that will calculate a hash on files and store the hash values. You can then recheck at any time to see if any bits have changed. I have used it on 300 GB at a time and use it for many data transfers and it works beautifully. Very easy to use, too. Note: it will READ your data and confirm that it is still all there but it won't re-write your data.

Perhaps get another disk and copy the "stale" disk to the "fresh" disk and then check with ExactFile to see that every single bit has transferred OK. Do that 3-4 times a year and you'll be OK. If the HDD isn't used for many months, it might start getting mechanically flaky (?). And keep a backup somewhere else too! Perhaps get a disk enclosure or caddy to swap disks.

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