Jump to content
Joe L.

A good, but bad disk... badblocks alone can never be trusted.

78 posts in this topic Last Reply

Recommended Posts

While I realize this is an old post, the data presented here has historical value in that badblocks, preclear and/or a full parity read scan cannot always reveal a potential problem with a hard drive.

 

Anecdotal Evidence

Notice how the smart short tests did not reveal the problem.

 

When checking the health of this drive I did the following procedure

 

smart short test

smart long test, Read failure.

4 pass badblocks pass 1 revealing problem, pass 2-4 did not reveal issue.

16 sectors reallocated at start, 30 sectors reallocated at end, no pending sectors.

Smart long test again, read failure in a different place.  No pending sectors. (now that surprised me)

4 pass badblocks, no errors reported, no sectors reallocated, no pending sectors.

smart long test passes.

 

What this reveals is that badlocks and/or preclear alone cannot detect or force the error to occur.

Nor can a full badblocks read or parity check read. 

It's probably more likely that a problem will be revealed with a full read, but in this case that did not happen until the smart long test occurred.

 

It's crucial to do the smart long test before inserting the drive into your array or someone may be unpleasantly surprised.

 

When inserting a drive into the array I always do

1. conveyance test (which tests mechanics) It's a manufacture test of potential shipping damage.

2. smart long test (marks a line in the smart log)

3. Check for issues in smart report

4. preclear or my own 4 pass badblocks of xaa,x55,xff,x00

5. check for issues in smart report

6. smart long test again (marks a line in the smart log)

7  check for issues and save smart report.

2015-10-21_17_55.17-edit.jpg.b6adc32e59ac923d9fac857de3cca678.jpg

Share this post


Link to post

 

Smart long test again, read failure in a different place.  No pending sectors. (now that surprised me)

 

 

Not what about this surprised you, but don't expect a device test to generate pending. The surface scan does not count as a IO request.

 

Your results don't show anything odd.

 

The first long test found error, the first pass badblocks did too. The first pass forced the sectors to reallocate, thus later passes found no more.

The second long test found an error. The second badblocks was able to read the sector (badblocks requests do get retried, long test does not), and and re-wrote it (several times) just like pass 2,3,4 above.

The third long test passed.

 

The question is, did you deem the drive, good, usable, or discard?

 

 

I live by badblocks, typically having it running on dozens of drives at any given time. I have seen similar behavior and now reserve such drives for special systems which can provide more frequent fault domain results. I don't put them back into production.

Share this post


Link to post

Smart long test again, read failure in a different place.  No pending sectors. (now that surprised me)

Not what about this surprised you, but don't expect a device test to generate pending. The surface scan does not count as a IO request.

Your results don't show anything odd.

 

Typically in my prior tests, when a surface scan fails with a read error the number of pending sectors is incremented.

At least with the drives I've used.

 

...

The question is, did you deem the drive, good, usable, or discard?

I'm tossing it.

 

I live by badblocks, typically having it running on dozens of drives at any given time. I have seen similar behavior and now reserve such drives for special systems which can provide more frequent fault domain results. I don't put them back into production.

I don't use them either.

Share this post


Link to post

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.