Event ID 7 The device has a bad block

These appear in the System log and for as much surfing as I've done on the topic I'm not clear on what Windows is telling me. Yes the hard disk drive (spinner) has bad blocks, but according to SMART and HD Tune and etc they are not yet at a critical stage, and AFAICT there is no impact to the day-to-day operation of the computer. But of course the errors in the log are disturbing.

I've done the chkdsk repair blocks thing which I *thought* would map the bad blocks out of operation, and subsequent runs of chkdsk declare everything's OK. So is it simply the case that once a drive has developed a bad block that Win7 somehow trips-over the thing forever? Or is ID 7 telling me that no amount of re-allocation or repair has worked and I need to replace the hard disk?

What happens is a bad block is found and at first it's realocated to engineering track only when that's full do you start to see them then windows marks them as bad so when you run check disk it doesn't look at them or report them. The disk is going to fail the only question is when

hi well if it was me I would not wait for the hard drive to fail I would just replace it as hard drives really do not cost that much

How did you run CHKDSK?

Did you run CHKDSK /f or CHKDSK /r ?

CHKDSK /r repairs bad sectors , whereas CHKDSK /f only recovers more minor errors.

samuria said:

What happens is a bad block is found and at first it's realocated to engineering track only when that's full do you start to see them then windows marks them as bad so when you run check disk it doesn't look at them or report them...

Well it seems that if Windows marks them as bad, such that chkdsk no longer reports them, then the Error that appears in the log should give a clue as to how to find them?

In other words, I find it odd that MS does not (apparently) have any utility to identify specifically how many bad blocks the HDD has.

Yes I know HDDs are cheap, but I do for example have a 4-bay NAS, one drive of which developed some 27 bad blocks a few years ago and then has never deteriorated from that.

I just don't want to copy to a new drive and throw the old one away without being clear about WHY.

You goto the disk makers website most offer a free test specific for their drives and that will give you a report

OK, I know that. I remain surprised and puzzled that Windows continues to report bad blocks that have been mapped-out.

The effect is simply that one becomes blind after a while to this error such that new bad blocks that might occur do no longer get the end-users' attention.

Not all bad blocks will be mapped out. If a bad block is found during a write operation the block can be easily mapped to a spare. But if the error occurs during a read operation it isn't so simple. An error means the contents of the block could not be reliably read. If that block were mapped out there would be no possibility of ever recovering that data. The drive won't do that. All the drive can do is make a note of the error. If the block is later read without error or it is written with known data then it can be mapped out. You have no way of knowing when or if either situation will occur.

I have little tolerance for drives with bad blocks. The number of bad blocks reported isn't necessarily the total number. The technology to continuously monitor for bad blocks does not exist. The only way to know about a bad block is when it is accessed. Another problem is that there may be some internal issue that is causing the bad blocks and it may get worse. 10 bad blocks today may be 100 tomorrow and 1000 the next.

Back in the 1980's you could pay $1000 for a 10 MB drive. With those prices it was easily justified to use a failing drive. But with current prices that makes no sense to me.

LMiller7 said:

I have little tolerance for drives with bad blocks.

I understand, and don't necessarily disagree. I was just looking for clarification and you have helped, thanks.

I thought that CHKDSK would, when asked to check for bad blocks, upon encountering one would mark it as bad, and then, if multiple read attempts failed, indicate in its log that it failed to recover some data. If successful in reading the data, that it took multiple reads meant that the bad block was mapped-out, and CHKDSK's post-run report would say something like "bad blocks were found but no data was lost".

To put it another way, yes CHKDSK might come across a block that could not "reliably" be read, but after multiple tries WAS read accurately, and then the block was marked as bad and the file written elsewhere. Hence my query about why Windows log continues to report, when CHKDSK is "happy".