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I heard that doing too many Low Level formats can damage the hard drive. But it make things really fast and remove almost all the malware infections. So, my question is, how many times can we do the low level format safely without damaging the hard drive?

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closed as not constructive by Xavierjazz, Indrek, 8088, Luke, Nifle Sep 6 '12 at 2:41

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2 Answers

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Lets start with defining what a low level and a high/normal level format is:

Normal format:

  • All sectors in a volume get written to with new data (e.g. empty block of zeros). Ergo all is wiped.
  • All sectors get written to, including previously undiscovered bad ones. These will get marked bad and modern drive will remap these to spare sectors.
  • Since all sectors get written to, this takes a long time.
  • It will not do damage to the drive.

Quick format:

  • The volume gets marked empty. Compare this to a book where you erase the index page
  • Little data gets written. The process is fast.
  • It will not do damage to the drive.

Low level:

  • The sectors on the entire drive get rewritten. (If you have multiple volumes on them then all will be lost)
  • If you have modern hardware the drive will probably refuse the command, or do nothing and return an 'OK' code. 52MB SCSI drives (yes, mega, not giga) are already considered modern. Any hardware still in use probably falls in this class.
  • If you manage to put the drive into a special factory mode and low level the drive then all data on the drive will be lost. This may include the drives firmware which sometimes is stored on disk. This will effectively kill the disk. (This differs per manufacturer and per model).
  • The low level is likely to take a long time. (I needed hours just to low level format old 4GB IBM drive when I was changing their 520 byte sectors to 512 bytes sectors.). It might also need a lot of other data, such as desired sector skew, track skew, head skew, spare sectors etc etc.

All this comes down to:

  • You probably do not want to low level any drive
  • I suspect that with low level format you mean a full normal/high level format.
  • A normal format will not do damage.
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with the possible exception of SSD. Writting on SSD's is destructive. – M Afifi Sep 4 '12 at 14:29
True. Writing to a SSD with a full high level format is a bad idea. Luckily we have the secure erase command instead. – Hennes Sep 4 '12 at 14:50
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Low Level Formatting, can't dmaage the hard drive. But if the hard drive is damaged already (eg Bad Sectors have been found), and there are not enough hot fix sectors, then it's possible that the drive could appear to have been damaged by the low level format.

Why?

There are a certain number of sectors set aside by the manufacturer. During the normal operation of the drive, a sector may "die", so the drive automatically maps in one of the reserved sectors, to replace the damaged one. So the drive will always appear to be "perfect".

If there isn't any more reserved sectors available, then you'll start to see bad sectors appearing.

Low Level formatting is one method to have the drive check all of the sectors, and is the most stressful for the drive. If a bad sector is going to appear, chances are it maybe during a low level format...

Thus, it's possible that a low level format could appear to damage a drive, when it's actually just revealing the existing issue.

  • Ben
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Programs like SpinRite can also help a HDD discover which sectors are good and which are bad. These same programs are also able to help the HDD actually determine if a sector can be recovered. – Ramhound Sep 4 '12 at 13:14
Low level format is not the most stressful, defrag is. – Moab Sep 4 '12 at 13:26
@Moab defrag most likely won't read & write all sectors of a volume. Blanking a disk (or volume) with a full read/write test will. – Ansgar Wiechers Sep 4 '12 at 13:51
@AnsgarWiechers Read-write is not stressful when it is contiguous sector by sector when doing a low level format, defrag is due to the fact the read-write arms are jumping all over the place, I have damaged more hard drives during a defrag, never on a low level format. I have done thousands. – Moab Sep 4 '12 at 14:51
A Defrag is more deadly? – EApubs Sep 4 '12 at 15:14

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