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I use HD Tune pro error scan to find problems with mechanical hard drives. However, I am confused as to weather these are fixable problems or not. Please clarify weather my statements are accurate:

Zero-Fill (manufacturer utility): Can permanently fix the drive by moving bad sectors with reserve space on the drive?

Full-Format: Can hide problems temporarily by marking blocks as bad in the filesystem? (this will be undone by a quick format)

Chkdsk (full scan): Same as a full format for marking purposes?

Comments regarding the danger of using drives with questionable sectors are outside the scope of this question

cloneman
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3 Answers3

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Zero-Fill

No, you can not at the same time say a bad sector is 'fixed' and 'moved' to reserved space. Fact bad sectors are 'moved' (of course nothing is actually moved) means they can not be fundamentally fixed or repaired, the drive is merely hiding 'grown defects'. IOW, such defects are permanently hidden.

Such reallocated sectors are tracked in SMART attribute 05. The RAW value represents the actual number of reallocated sectors.

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Full-Format

A 'full format' in itself means nothing if you do not also tell what you do the 'full format' with: So, what OS or utility are you using to perform a full format. Older Windows versions for example did a read-only scan to detect read issues and flag at the file system level, while newer Windows versions actually zero fill a volume when performing a full format. If the latter runs into a 'pending sector' it should trigger the drive itself to reallocate the sector.

IOW, a full format using a modern Windows version can achieve the same as a so called 'zero-fill', it is in fact a zero-fill, and can permanently hide defects (trigger reallocation).

Chkdsk

Chkdsk to my knowledge performs a read-only test. Unless the drive silently reallocates a sector on read, the cluster to which the sector belongs is marked bad at the file system level. For example FAT file systems keep track of bad clusters in the file allocation table(s), NTFS maintains a list in the $BADCLUS file.

NTFS maintains a number of meta files, $BADCLUS being on of them

Of course chkdsk disk needs to write to the drive to update file system meta data, but the surface scan itself is read-only. Chkdsk can be requested to re-evaluate bad clusters, so re-read them and remove them from a bad cluster list and put them back in use in case there are no read issues (for example due to bad sectors being reallocated).


With regards to 'Low Level Disk format', there is no such thing that can be performed outside the factory. Tools that pretend to perform a low level format type of thing simply write for example zeros to the drive.


How does sector reallocation work?

If you understand how drives reallocate sectors you can answer your own questions once you know what the utility you use actually does (read-only vs. read/write or write (zero-fill) scans).

First of all we assume a drive keeps a pool of spare sectors outside LBA space. LBA space are the sectors we can actually address. Sector reallocation is map one sector from LBA space to non LBA space, while we map a spare sector from non LBA space to LBA space.

Conventional drives, spinning CMR drives typically maintain a fixed number of sectors, in number and location that they can use to remap bad sectors while drives that more dynamically map sectors, like SSDs or SMR drives could use any sector outside LBA space to remap a bad 'sector' (SSDs can not remap sectors, they need to remap so called erase blocks).

Conditions that can cause a drive to remap are:

Non-recovered write errors

When a write operation can not be completed after the Error Recovery Procedure (ERP) is fully carried out, the sector(s) are reallocated to a spare location.

Recovered read errors

When a read operation for a sector fails once and then is recovered at the specific ERP step, this sector of data is reallocated automatically.

Non-recovered read errors

When a read operation fails after a defined ERP (error recovery procedure) is fully carried out, a hard error is reported to the host system. This location is registered internally as a candidate for the reallocation.

IOW the drive will report a problem to user in this case!

You can observe such an event using a S.M.A.R.T. utility, in ‘pending sectors’ attribute.

When a registered location is specified as a target of a write operation, a sequence of media verifications is performed automatically. When the result of this verification meets the criteria, this sector is reallocated.

In this case the SMART pending raw value drops, reallocated value increases.

IOW, you can now answer your own question ..

For example, a full format using a more recent Windows version will cause non recovered write errors and pending sectors to be reallocated as it zero fills a volume prior to format, while a read-only type full format (using pre-Vista Windows versions) will not.

But none of te methods will truly fix or repair bad sectors.

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Zero Fill writes the disk with Zero's. It does not move data around, it tries to delete it ! You probably can't zero out bad sectors though, so it does not always get all the data (but will get almost all of it).

Full Format - Checks drive for errors and maps around those.

Chkdsk - looks for, and attempts to correct file system corruption. Depending on the filesystem and chkdsk utility this may or may not mark sectors bad.

You are missing an option - Low Level Disk format - this will remap the bad sectors at the lowest level of the disk. This is what you need to do if you are trying to fix a damaged disk.

Its a bit concerning that you assert bad that comments about the danger of using drives without questionable sectors is outside the scope of this question. This is really key - as only someone who does not understand, does care about their data, or if onselling, there reputation, would even consider doing anything with a hard drive developing bad sectors other then pull the data off and replacing it.

davidgo
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For commercially available software such as HD Tune pro, there are 3 'official' answers to your question as of 2024:

  • Zero-Fill (manufacturer utility): Yes, it can permanently fix the drive by moving bad sectors to reserve space on the drive.

  • Full-Format: Yes, it can hide problems temporarily by marking blocks as bad in the filesystem. This marking is undone by a quick format.

  • Chkdsk (full scan): Yes, it functions similarly to a full format for marking bad sectors.

Max Haase
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