Do the bad blocks preventing me mount my system HD mean I need to replace it?

I have asked this question elsewhere in a different way but didn't get much help - since then I've ran a few more tests and can hopefully zero in on the issue.
I have a 3TB fusion drive late 2012 model 27" iMac that started behaving sluggishly - transferring things from folder to folder in Finder would bring up the spinning beachball (luckily I managed to transfer my important files). When I ran Disk Utility it said that 't stopped verifying "MacintoshHD" and this disk needs to be repaired using the Recovery HD'. I did the restart and attempted the repair and got the message that DU couldn't repair the HD, backup files and reformat the disk. When I attempted to do this I then got the window "Disk Erase failed with the error: The given file system is not supported on Core Storage". The image of the HD also disappeared from view so I can't do anything... not reformat, reinstall Yosemite etc
I ran Tech Tools ProToGo from a USB drive and it showed I had 90 bad blocks on my HD (not the SSD part) but the repair button was greyed out.
I like to think I'm relatively competant with self repair/diagnosis but I've hit a brick wall here. The jury seems to be out whether bad blocks are an indication that the HDD has to be replaced - I've read conflicting reports in these very forums.
FTR I installed Yosemite on an external HD and am using my iMac that way so I guess a lot of stuff under the hood continues to work perfectly.
I would really appreciate any advice.
I've included a couple of relevant pics below; here's the link from my previous question that has a lot more pics and info if anyone wants to have a look Total HD crash - how to get the files

I've tried reading through both threads but am not quite able to follow along....one thought though, have you tried using OS X Internet Recovery?
OS X: About OS X Recovery - Apple Support maybe the Utilities there will allow you to repair the hard drive.

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How does the filesystem handle bad blocks?

Let's suppose your hard drive develops a bad sector on it. What happens?
I remember early products where the OS would constantly try to store new files right on top of the bad block, find the file couldn't be written/verified, then would write it elsehere... then the next time it would do the same thing again, expecting the block to "heal" I guess
What happens on MacOS (extended, journaled) if it's writing a file and finds a bad block in freespace? Does the OS know how to "cocoon off" or tag the bad block as bad and not use it?
Now what happens if the bad block develops underneath an active file? What's the recovery pattern? Or is there none - does it just leave the block bad permanently? Is there any way to fix that?

Boot your computer from the DVD that came with it, and use Disk Utility to check the status of the disk. Select the disk and look at the S.M.A.R.T. status at the bottom. If it displays anything other than Verified, then the disk isn't going to last much longer.
Modern hard disks don't develop "bad sectors" that the OS needs to handle. The disk drive itself automatically remaps bad sectors to spare unused sectors in a way that is transparent to the OS. When too many of those bad sectors are remapped, the S.M.A.R.T. status will report an error.
What you're describing is a failing disk. It's more than likely the early stages of a total failure, rather than just a bunch of bad sectors. Same thing happened to my MacBook a few months ago. After about two hours, it failed completely. I picked up a new drive on the way home, and restored it from Time Machine overnight. The only data that I lost was an iTunes purchase that I made that morning (iTunes Support let me download it again). You have a backup, right?
It's also possible that you've either run out of free space on the startup disk, or you have a process running that's consuming too much CPU and/or RAM resources. If that's the case, a reboot will clear it (until whatever caused it happens again).

Correcting a bad block on ext4 and with GTP partition table

Hello,
I ran a SMART offline test today which came back as a bad block:
# 1 Extended offline Completed: read failure 30% 8363 3212759896
This is my first run-in with a bad block, and since these drives are big and relatively new, I want to be proactive and fix any problems as they arise. Here is my setup:
* I have 2x 2TB HDDs of same make and model, with the device link being /dev/sdc and /dev/sdd. /dev/sdc is the one with the error.
* These two disks are linked via a Linux RAID 1 array under /dev/md0 which is then mounted on /storage.
* Both drives have only 1 partition under a GUID Partition Table (GPT)
I've looked around to try to find info on fixing bad blocks, and I came across this: smartmontools.sourceforge.net/badblockhowto.html
However, it seems to be out-dated and geared for tools like fdisk (which I cannot use for GPT) and filesystems ext2/3 (although, due to the backwards compatibility, I'm sure it works with ext4 as well), and a lot fo the commands gives things like "Couldn't find valid filesystem superblock."
Can someone point me in the right direction as to how I can fix this issue?
EDIT:
My noob is showing. I got the commands above to work, and when I check to see which file is using the bad block it shows this (after all the calculations involved, the block was 401594731):
debugfs: icheck 401594731
Block Inode number
401594000 <block not found>
So i'm assuming that there isn't a file assigned to it (empty space?). But then, when I use dd to read from it, it seems to read just fine:
sudo dd if=/dev/md0 of=my.block skip=401594731 bs=4096 count=1
1+0 records in
1+0 records out
4096 bytes (4.1 kB) copied, 0.0222587 s, 184 kB/s
I think it's able to read it since the other disk in the RAID1 array doesn't have the bad block. But I just want to make absolutely sure that there is no file assigned to that block before I nuke it. Given the above information, would it be safe to remove this block from service?
Last edited by XtrmGmr99 (2012-01-26 01:17:51)

Yes I think the block is not in use. You can do
debugfs: testb 401594731
which will state it clearly ("not in use" vs "marked in use")

How to keeps track of new coming bad blocks on a hdd

I have some 2,5 hdd lying around and wanted to test them for bad blocks and found that I can use Badblocks for this.
But how do I keep the "list" of bad blocks up-to-date if new bad blocks are detected, or is this not posseble?
Solixxx
Last edited by solixxx (2013-09-30 23:48:21)

graysky wrote:You can detect and lock out bad ones... but the danger is not knowing which good blocks will go bad in the future. I have a hdd in an old machine that has bad blocks on it... been running fine for 9+ months now after isolating them.
Exactly :-)
I've been using a drive with isolated bad blocks for over a year now, but I store only data I don't care that much about - I can re-download or recreate it.
I thought you just wanted to list the bad blocks. If you're going to reformat the device, it is the mechanism of isolating the bad blocks I wrote about, so you should be OK.
I think badblocks prevents the bad block from being used by the filesystem, but they still reside on the device, so if you run badblocks again, it should list both the old bad blocks and any new ones too.

Does DU (11.0) update a drive's bad block map?

I have an external drive (an old WD 256Gb I pulled form a Tivo) that I suspect has bad blocks. Does Disk Utility (11.0 as provided with 10.5.2) update the bad block map so that this drive may become reliable?

Only if you format the drive using the Zero Data option. You will also need to repartition the drive:
Extended Hard Drive Preparation
1. Open Disk Utility in your Utilities folder. If you need to reformat your startup volume, then you must boot from your OS X Installer Disc. After the installer loads select your language and click on the Continue button. When the menu bar appears select Disk Utility from the Installer menu (Utilities menu for Tiger or Leopard.)
2. After DU loads select your hard drive (this is the entry with the mfgr.'s ID and size) from the left side list. Note the SMART status of the drive in DU's status area. If it does not say "Verified" then the drive is failing or has failed and will need replacing. SMART info will not be reported on external drives. Otherwise, click on the Partition tab in the DU main window.
3. Click on the Options button, set the partition scheme to GUID (only required for Intel Macs) then click on the OK button. Set the number of partitions from the dropdown menu (use 1 partition unless you wish to make more.) Set the format type to Mac OS Extended (Journaled.) Click on the Partition button and wait until the volume(s) mount on the Desktop.
4. Select the volume you just created (this is the sub-entry under the drive entry) from the left side list. Click on the Erase tab in the DU main window.
5. Set the format type to Mac OS Extended (Journaled.) Click on the Options button, check the button for Zero Data and click on OK to return to the Erase window.
6. Click on the Erase button. The format process will take 30 minutes to an hour or more depending upon the drive size.
Steps 4-6 are optional but should be used on a drive that has never been formatted before, if the format type is not Mac OS Extended, if the partition scheme has been changed, or if a different operating system (not OS X) has been installed on the drive.

A single bad block

Hi,
I am a Graphic Designer from Nepal. I have a single bad block on my 7 month old macbook pro 2011. It hasn't been written over yet with spare as my HD is almost full. Should i wait it to be written over with spare block or should i go on ahead with format. Will it damage more blocks if i wait? i would have returned it but it will cost me more to return it as i will have to sent it abroad as there is no apple stores here (only authorized dealers). It's a single bad block which is not that bad and can happen from the factory. I have even heard many hard disk manufacture dont even exchange it if there is just few bad blocks as it is quite normal. My main question is should i wait for bad block to be written over with spare or should i format it with zeros? thanks in advance.

You ran some driver checking software and it located a bad block, no big deal because all drives have bad blocks.
When your computer attempts to write to the bad block and can't verify it, then it writes the data to a new location and that bad block is mapped off.
This occurs automatically and requires absolutely no assistance from you what so ever.
So don't do anything, it's been all taken care off. If you do, your just wasting your time and could erase your data.
The software your running is for technical use only, just go about using your computer like before and nothing will happen from the bad block.

Disk Utility: for bad blocks on hard disks, are seven overwrites any more effective than a single pass of zeros?

In this topic I'm not interested in security or data remanence (for such things we can turn to e.g. Wilders Security Forums).
I'm interested solely in best practice approaches to dealing with bad blocks on hard disks.
I read potentially conflicting information. Examples:
… 7-way write (not just zero all, it does NOT do a reliable safe job mapping out bad blocks) …
— https://discussions.apple.com/message/8191915#8191915 (2008-09-29)
… In theory zero all might find weak or bad blocks but there are better tools …
— https://discussions.apple.com/message/11199777#11199777 (2010-03-09)
… substitution will happen on the first re-write with Zeroes. More passes just takes longer.
— https://discussions.apple.com/message/12414270#12414270 (2010-10-12)
For bad block purposes alone I can't imagine seven overwrites being any more effective than a single pass of zeros.
Please, can anyone elaborate?
Anecdotally, I did find that a Disk Utility single pass of zeros seemed to make good (good enough for a particular purpose) a disk that was previously unreliable (a disk drive that had been dropped).

@MrHoffman
As well pointed your answers are, you are not answering the original question, and regarding consumer device hard drives your answers are missleading.
Consumer device hard drives ONLY remap a bad sector on write. That means regardless how many spare capacity the drive has, it will NEVER remap the sector. That means you ALWAYS have a bad file containing a bad sector.
In other words YOU would throw away an otherwise fully functional drive. That might be reasonable in a big enterprise where it is cheaper to replace the drive and let the RAID system take care of it.
However on an iMac or MacBook (Pro) an ordinary user can not replace the drive himself, so on top of the drive costs he has to pay the repair bill (for a drive that likely STILL is in perfect shape, except for the one 'not yet' remaped bad block)
You simply miss the point that the drive can have still one million good reserve blocks, but will never remap the affected block in a particular email or particular song or particular calendar. So as soon as the file affected is READ the machine hangs, all other processes more or less hang at the same moment they try to perform I/O because the process trying to read the bad block is blocking in the kernal. This happens regardless how many free reserve blocks you have, as the bad block never gets reallocated, unless it is written to it. And your email program wont rewrite an email that is 4 years old for you ... because it is not programmed to realize a certain file needs to be rewritten to get rid of a bad block.
@Graham Perrin
You are similar stubborn in not realizing that your original question is awnsered.
A bad block gets remapped on write.
So obviously it happens at the first write.
How do you come to the strange idea that writing several times makes a difference? How do you come to the strange idea that the bytes you write make a difference? Suppose block 1234 is bad. And the blocks 100,000,000 to 100,000,999 are reserve blocks. When you write '********' to block 1234 the hard drive (firmware) will remap it to e.g. 100,000,101. All subsequent writes will go to the same NEW block. So why do you ask if doing it several times will 'improve' this? After all the awnsers here you should have realized: your question makes no sense as soon as you have understood how remapping works (is supposed to work). And no: it does not matter if you write a sequence od zeros, of '0's or of '1's or of 1s or of your social security number or just 'help me I'm hold prisoner in a software forum'.
I would try to find a software that finds which file is affected, then try to read the bad block until you in fact have read it (that works surprisngly often but may take any time from a few mins to hours) ... in other words you need a software that tries to read the file and copies it completely, so even the bad block is read (hopefully) successful. Then write the whole data to a new file and delete the old one (deleting will free the bad block and ar some later time something will be written there and cause a remap).
Writing zeros into the bad block basically only helps if you don't care that the affected file is corrupted afterwards. E.g. in case of a movie the player might crash after trying to display the affected area. E.g. if you know the affected file is a text file, it would make more sense to write a bunch of '-' signs, as they are readable while zero bytes are not (a text file is not supposed to contain zero bytes)
Hope that helped ;)

How to repair a bad block on internal hard drive?

I've just performed a surface test on my internal HD
It reports back one bad block, at # 1, 118, 671, 700.Filename = N/A.
1. Should I be concerned about this? I have not noticed any performance issues.
2. If I wanted to get rid of it anyway, how do I repair that bad block?
Please advise.
Many thanks.
/gh

Good to know this happens automatically.
Is that something OS X automatically does on startup, or on shut down, or in background?
But in this case, that automatic feature seems to have missed this block. Else the bad block would not show up in the utility, with a file in it.
Or ,,,,perhaps it still shows up as a bad block in the utility, even though it's been mapped out.
If that's the case, then I guess I need another kind of utility that would report the block has been mapped out....
Any suggestions?

Bad blocks on an external drive, and disk tools for a MacIntel...

I'm having a problem with my external drive which was pulled from my 12" PBook G4 and put into a USB 2.0 enclosure. When I try to transfer data from my internal HDD it runs for a bit, then, it just stops... no spinning ball and it won't allow me cancel the copy. If I fuss with it long enough (clicking on as many finder features as possible), the Finder will eventually stop responding.
I ran Drive Genius as it was the only software I could find that would work as on my computer. Using the "Scan" function, it came back and told me that I had several bad blocks (I had to stop the scan at 115 because I needed to restart my computer). In the program's help guide, it said that it cannot do anything about the bad blocks, and I may need to reformat.
So, I reformatted using Disk Utility on my system start-up disk (not the disk that came with the compuer), then I tried to zero-out all data. Spinning beach ball and the application stopped responding.
Is it possible to quarantine bad blocks if they can't be reformatted or zeroed out on a MacIntel?
Thank you kindly for any help.

Sorry for the additional posts, I don't know how to edit my last post...
Disk Utility is still at 49 minutes remaining, and it's been almost an hour. Still letting it run, and hoping for the best.

How to recover data from a hard drive with bad blocks?

An external hard drive, 4TB Iomega...connected via eSATA cable...had a power outage and the drive won't be read by OSX now. (Yes, it was on a surge protector and no I did not have a backup. I was actually preparing for the process of creating a backup when the power went out!) Anyway, I have tried using Data Rescue 3 and DiskDrill to try and recover data from the drive. I can recover the first 1/3 of the drive, but it ejects when either app tries to access the bad block. Can anyone tell me how/what software to use to recover the data? I know there are programs that will avoid the bad block but I've only found them for Windows. Are there any that will do such a thing in Lion? Any help will be appreciated...and no, I can not afford a data recovery service. Trying to do this on my own.

Basics of File Recovery
If you stop using the drive it's possible to recover deleted files that have not been overwritten by using recovery software such as Data Rescue II, File Salvage or TechTool Pro. Each of the preceding come on bootable CDs to enable usage without risk of writing more data to the hard drive. Two free alternatives are Disk Drill and TestDisk. Look for them and demos at MacUpdate or CNET Downloads.
The longer the hard drive remains in use and data are written to it, the greater the risk your deleted files will be overwritten.
Also visit The XLab FAQs and read the FAQ on Data Recovery.

Suggestions for formatting external drive with bad block?

I have a OWC Mercury 300 GB external drive. I wanted to erase it and use it as a backup for one of my laptops. The drive had been working fine as a Time Machine back up for an old (intel) iMac. I told Disk Utility to erase and reformat. It erased, but refused to reformat saying there was a bad block on the drive. Now Disk Utility recognizes the external drive but won't do anything with it. No Verify. No Repair. All grayed out. Any suggestions?

I wasn't a hard error, that's why. Repartitioning and reformatting will often fix soft errors in the directory structure. Had there been a real, new, bad block on the drive it would not be repairable. A soft bad block error can be fixed by reformatting. The hard block error may be fixable by using Zero Data one pass that may spare out the bad block. But if none of that works then you need to replace the drive.
You were fortunate that the error probably was spurious and resolved by repartitioning (may have been in the disk's RDB.)

ORA-01578 - bad blocks.

Hello,
We had a SAN crash last month and with all the confusion I missed that we had some bad blocks after the crash. Our RMAN backups have now aged out so we don't have a RMAN backup. What I do have is a datapump backup from before the event. This is table corruption. Is there a way to either restore the table to a stage location, catalog the table or datafile somehow, then restore the bad block? Otherwise, somehow determine the bad data and get the data from the backed up table and insert it back into the bad table after I re-recreate it without the bad blocks?
Oracle support is just saying recreate the table skipping the bad blocks but there has to be some way here if the data is on that datapump backup that I can determin what it is then restore it.
Thanks

The fix blocks procedure did not work and I have not attempted the skip blocks. If I run the skip corrupt blocks will my query work? Is that worth a shot next?
select count(*) TRACKING_ID from JEBCS3NM.TRACKABLE_OBJECT t, JEBCS3NM.CONVEYANCE c where c.TRACKABLE_OBJECT_GUID = t.TRACKABLE_OBJECT_GUID and PRIMARY_MOVER_ID is null
ERROR at line 1:
ORA-01578: ORACLE data block corrupted (file # 75, block # 1024073)
ORA-01110: data file 75: '/u02/oradata/bcso/jebcs3nm_d.dbf'
SELECT OBJECT_NAME, BLOCK_ID, MARKED_CORRUPT
2       FROM REPAIR_TABLE;
OBJECT_NAME                      BLOCK_ID MARKED_COR
CONVEYANCE                        1024073 TRUE
CONVEYANCE                        1024105 TRUE
CONVEYANCE                        1024113 TRUE
SQL> SET SERVEROUTPUT ON
SQL> DECLARE num_fix INT;
2 BEGIN
num_fix := 0;
DBMS_REPAIR.FIX_CORRUPT_BLOCKS (
     SCHEMA_NAME => 'JEBCS3NM',
6       OBJECT_NAME=> 'CONVEYANCE',
7       OBJECT_TYPE => dbms_repair.table_object,
     REPAIR_TABLE_NAME => 'REPAIR_TABLE',
     FIX_COUNT=> num_fix);
DBMS_OUTPUT.PUT_LINE('num fix: ' || TO_CHAR(num_fix));
END;
12 /
num fix: 0
PL/SQL procedure successfully completed.

Do the bad blocks preventing me mount my system HD mean I need to replace it?

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