[ale] possible to use hard drives that have bad blocks ?

[Courtney Thomas]

Thanks Greg.

This is all new to me and quite interesting.

I took the first drive that had [at least] one bad block, and did a:

dd if=/dev/zero of=/dev/hdX

and then:

dd if=/dev/hdX of=/dev/null

and now see NO errors, whereas previous to this write I got an error.

Does that mean that the drive is now....all right ?

Cordially,
Courtney


On Mon, 2005-06-27 at 08:47, Greg Freemyer wrote:
> Not really.
> 
> Blocks (sectors) slowly fail on disks over time.  Not much you can do
> about that, and it is pretty much true of all drives.
> 
> I have read that you should write to every sector at least once every
> 5 years because the magnatism slowly fails, and after 5 years the
> sectors need a re-fresh.
> 
> If your worried about cost and want to save a disk, you can do a dd
> if=/dev/zero of=/dev/hdX to refresh the drive.  Who knows it may last
> another 5 years.
> 
> For true block failures as opposed to magnetic degradation, the blocks
> are only tested by the drive logic on write, so if you have a sector
> that is never written and it goes truly bad, you will have a single
> bad sector for the remaining life of the drive.
> 
> Performing a write to the sector not only refreshes the magnetic
> field, it allows the drive to recognize the failed sector and "do its
> job" by re-assigning the bad sector to a good sector from an internal
> reserved bad sector list.
> 
> I suspect RAID logic is used as much to protect from these isolated
> block failures as much as it is for a true disk failure.
> 
> OTOH, if you write to the sector and it remains bad, then you more
> than likely have a drive on its way out the door.
> 
> FYI: High-end RAID systems can monitor the disk sector failure rate
> and once the failure rate exceeds a given rate, they can pro-actively
> declare the drive failing.  HP for one accepts this designation as a
> valid reason to swap a drive if you are a supported customer.
> 
> Greg
> 
> On 6/26/05, Courtney Thomas <ccthomas at joimail.com> wrote:
> > Makes sense :-)
> > 
> > Thanks,
> > Courtney
> > 
> > 
> > On Sun, 2005-06-26 at 11:40, Jim Lynch wrote:
> > > As cheap as disks are these days, if this is an internal 3.5" drive, I'd
> > > replace it.  If one block is bad, how long before another one goes?
> > >
> > > Jim.
> > > Courtney Thomas wrote:
> > >
> > > >I've got a couple of HDs that when I:
> > > >
> > > >dd if=/dev/hdX of=/dev/null bs=1m
> > > >
> > > >I get a single instance of something like:
> > > >
> > > >FAILURE - READ_DMA status=51 <READY, DSC, ERROR> error=40
> > > ><UNCORRECTABLE> LBA=19194112 Input/output error
> > > >
> > > >My question is: does this signify a single bad block and is there a way
> > > >to identify this error to some program that can block it's use, so the
> > > >drive can be used ?
> > > >
> > > >Thank you,
> > > >Courtney
> > > >
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