RAID-1 and bad sectors?

"Rod Speed" wrote in message
wrote Rod Speed wrote

Use Everest to check the SMART data for the drive, post it here.
http://www.majorgeeks.com/download.php?det=4181

I just installed this, and under Storage SMART,
it doesn't show anything. It's all gray.

Yeah, you can get that result on some systems.

Particularly those where the S.M.A.R.T. driver isn't installed or
the driver isn't S.M.A.R.T. compatible.
Usually the RAID drivers are not.


There's another that isnt too bad on the knoppix bootable CD.

Not as easy to use by quite effective. Bit more difficult to post
the results with that tho if you dont know anything about linux.

See what SHDIAG says first.

And when I right click on SMART, it let's me do
a Quick Report, but it prints stuff out about various
other devices and nothing about the hard drive.

"philo" wrote in message
wrote in message ...
I just used BootItNG to resize the 2 NTFS partitions on my hard disk. I was
increasing the size of the C drive, so I had to shrink the D drive and slide
it down to the end of the disk. When I did the slide operation, I told it to
slide everything including the unused areas. I ended up getting an "error
reading from hard disk" message. So I retried the slide operation, but just
told it to slide the data only. That worked, so maybe there was a bad sector
in an unused area?


Go to the website of the HD's mfg and download the diagnostic utility
and run it.
If *any* errors are found..backup your data and replace the disc.


At any rate...I'd never use a drive with bad sectors in a RAID situation

Obvious lie. There is no such thing as a drive without bad sectors.

wrote in message
On Sat, 31 Dec 2005 17:46:49 +1100, "Rod Speed" wrote:

I also need to determine how BootItNG deals with writing data to bad sectors,

The hard drive should handle that behind BootItNG's back.

and how Windows deals with reading and writing data from bad sectors.

The hard drive should handle the writing behind Win's back.


So the hard drive will detect a bad sector and then find a good sector
to which to write the data?

Kind of.

Based on what Chuck F. said, the hard drive will
just write the data to whichever sector, even if its bad.

Basically yes, if it doesn't know about it being bad.
No, if the sector is a socalled bad sector candidate.
Then it will be write-checked and reallocated if necessary.



What will the SMART data tell me?

Basically confirm that the drive is dying.

Seems like a safe assumption.


I have no confidence that my new SP1213N
won't develop the same problems.

None of mine have. And the storagereview reliablity database
shows that plenty dont have any problems with their drives too.

And the result with many of their competitors drives are
much worse, particularly the maxtor drives of the same size.

The seagate 7200.7s do better, but the 7200.8s are obscenely bad.

Thanks for pointing out storagereview.com. Looks like the Samsungs are near
the bottom third. The Seagate 7200.7s are near the top. Maybe I'll get a
couple of those.

"Chuck F. " wrote in message
wrote:

I just used BootItNG to resize the 2 NTFS partitions on my hard
disk. I was increasing the size of the C drive, so I had to
shrink the D drive and slide it down to the end of the disk.
When I did the slide operation, I told it to slide everything
including the unused areas. I ended up getting an "error
reading from hard disk" message. So I retried the slide
operation, but just told it to slide the data only. That
worked, so maybe there was a bad sector in an unused area?

Which may mean that you wrote some of your actual data into a
failing "unused" area,

It wouldn't be unused then, now would it.

and that that data is now lost or altered.

Yup, that's why it is called "unused".

I wouldn't trust anything that was on that partition.

wrote in message
I just used BootItNG to resize the 2 NTFS partitions on my hard disk. I was
increasing the size of the C drive, so I had to shrink the D drive and slide
it down to the end of the disk. When I did the slide operation, I told it to
slide everything including the unused areas. I ended up getting an "error
reading from hard disk" message. So I retried the slide operation, but just
told it to slide the data only. That worked, so maybe there was a bad sector
in an unused area?

Anyways, I'm now ready to set up RAID-1 in my system. But I'm wondering if
that bad sector might cause a problem in a RAID-1 setup?

I know RAID-1 is supposed to help you if a drive fails.

And there are lots of broken products on the market that fail miserably when
actually taken to task.

But what if a drive doesn't totally stop working...
what if it only develops a few bad sectors?

Can RAID-1 handle that?

Common sense says that it should with last decade drive technology. But OSes
and drivers still basically behave the same as 10-20 years ago, so who's to say.
Common sense is often lacking in RAID products.

(I'll be using the HighPoint 370 controller on my Abit KT7-RAID motherboard.)

Like what would happen if the RAID controller is writing some data, and one of
the drives is OK but the other drive has some bad sectors on it?

Bad sectors should only matter on reads and corrected by data from the 'perfect' drive.

Can the RAID controller detect the bad sectors and write the data to good sectors?

No, unless it reads all data back that it writes, which is very inefficient and therefor
doesn't happen.

Or will it not detect the bad sectors and the 2 drives will be out-of-sync?

Yes and no.
Badly written data will not be detected until the next read to that data so until
that time the drives will not be out of sync even though technically they are.
Harddrives do not write-check on standard writes.
With write caching enabled they don't wait for writes to finish even.

"Arno Wagner" wrote in message
In comp.sys.ibm.pc.hardware.storage wrote:
I just used BootItNG to resize the 2 NTFS partitions on my hard
disk. I was increasing the size of the C drive, so I had to shrink
the D drive and slide it down to the end of the disk. When I did
the slide operation, I told it to slide everything including the
unused areas. I ended up getting an "error reading from hard disk"
message. So I retried the slide operation, but just told it to
slide the data only. That worked, so maybe there was a bad sector
in an unused area?

Anyways, I'm now ready to set up RAID-1 in my system. But I'm
wondering if that bad sector might cause a problem in a RAID-1
setup? I know RAID-1 is supposed help you if a drive fails. But
what if a drive doesn't totally stop working... what if it only
develops a few bad sectors? Can RAID-1 handle that? (I'll be using
the HighPoint 370 controller on my Abit KT7-RAID motherboard.) Like
what would happen if the RAID controller is writing some data, and
one of the drives is OK but the other drive has some bad sectors on
it? Can the RAID controller detect the bad sectors and write the
data to good sectors? Or will it not detect the bad sectors and the
2 drives will be out-of-sync?


It will detect a bad sector only if it reads from it. In that case
it will fail-over to the other disk. Many RAID controllers will
also mark the disk as bad and kick it form the array. If you
have bad sectors on eiter disk in different places that behaviour
is not too desirable, but in this case you are in trouble anyways,

since modern disks only exhibit bad sectors if they are dying or
have very serious problems.

Ignore the blithering idiot.
Bad power supply or overheating can cause these symptoms where the drive is not at fault.


Now, you might be in this situation and then your best bet is
possibly RAID recovery software (have seen some, don't remember
where) or if your controller allows you to disable the kicking on
defects. Linux software RAID seems not to allow you to do that.
What I would do in such a case is to mount both partitions/drives
read-only, determine which has less bad sectors, write them
down and copy that partition/drive to a good one. Then copy
the bad sectors on the first drive from the second one. If
ithe number of bad sectros is high, then script this using,
e.g., badblocks and dd_rescue.

When writing to a bad sector, the data will be written to both drives.
Since the data is written with checksums,

then the controller will recognize a bad sector and read it form the
other disk.

Nonsense, that is what the RAID driver will do.

See also above.

Arno