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Is there a limit to the number of times I can format a hard disk?

I tried to find this information on Wikipedia, but I didn't find an answer.

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    You can format a HDD as many times as you want until it fails. You can format a SSD until you exceed the maximum writes on the device.
    – Ramhound
    Feb 4, 2015 at 15:28
  • Currently there is no limit for formatting the hard disk but frequent format may harm the hard disk depend on the format you are doing like bios
    – BDRSuite
    Feb 4, 2015 at 15:30
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    @vembutech - What? Can you please explain your comment?
    – Ramhound
    Feb 4, 2015 at 15:43
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    Hard disks (and other things) have a Mean Time Before Failure (MTBF). Usually it says n hours before MTBF. What does that mean? Nothing. The disk can fail the next day you bought it or it can still work when you buy your next computer that doens't support the disk's interface anymore. You can only rely on one thing: it fails just that moment, when you want to make a backup and the previous was 3 month ago. That's why it's called Mean.
    – ott--
    Feb 4, 2015 at 18:33
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    @ott correction: it's called mean because the gremlins that go around breaking hard disks are jerks.
    – corsiKa
    Feb 5, 2015 at 20:22

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With the exception of CDs, DVDs and Blu-Ray discs (collectively called "optical media"), formatting is not a special action, and is fundamentally the same as any other disk operation. Formatting a storage device (whether it's a hard drive (HDD), solid state disk (SSD), or flash drive) just involves regular old reads and writes to the disk.

The only matters of concern are:

  • Are you performing a quick format or a full format? A quick format just overwrites the core filesystem data structures with a new filesystem, and usually only involves a few megabytes of writes (compared to many gigabytes or terabytes of total disk space). A full format only writes a small amount of data, but reads from every part of the disk to make sure the disk is OK.
  • Usually after you format a disk, if it's your primary storage, you're going to install an operating system on it. This usually causes between 2 and 25 GB of disk writes at first, plus another several gigabytes to install programs and updates.

All this writing of new data (which will vary in quantity depending on what type of format you performed and what you're going to do after you format it) can cause wear on SSDs, and to a lesser degree, the mechanical parts of HDDs. The amount of wear is proportional to the amount of data that is being read/written, with SSDs largely unaffected by reads, but HDDs being affected roughly the same by reads and writes.

I'm not going to delve into the topic of disk endurance and how certain quantities and frequencies of reads and writes affect the endurance (wear level) of different types of disks. This is a very complex topic that is completely independent from the subject of disk formatting.

Just know that the operation of reinstalling Windows on a hard disk is basically doing the same thing to your disk as copying several gigabytes of movies or pictures or music. Just the act of using a computer involves very frequent disk reads and writes.

The only difference is that formatting a disk and then using it often incurs a fairly large amount of reads and writes compared to what a typical user might do in a day.

Analogy: if you normally drive 8 km to work every day in your car, and then take a holiday trip of 200 km, this is fundamentally the same action -- you're just driving further. Formatting causes more wear on your disk, just like driving further causes more wear on your car.

If you want to know how reading and writing data impacts the endurance of your particular type of disk, you can either ask a new question, or search for existing questions (or use Google) to find this information.

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    Full format also wipes since Windows Vista.
    – Daniel B
    Feb 4, 2015 at 18:11
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    @DanielB in this case we don't mean a "secure wipe," but that zeros are written to the disk.
    – I say Reinstate Monica
    Feb 4, 2015 at 19:24
  • @DanielB - Thanks for that link. I was not aware that Windows' format behavior had changed as of Vista. I will edit my answer accordingly.
    – Wes Sayeed
    Feb 4, 2015 at 19:47
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    It may be of interest to note that a quick format doesn't necessarily overwrite any parts of the existing filesystem. It is only guaranteed to write a new filesystem while ignoring any existing one - depending on how the existing one is structured, it may overwrite all, some or even none of it. (This is more important if you want to recover data after a quick format - there's a good chance of at least some parts of the original FS still existing, perhaps enough to make recovery easier.)
    – Bob
    Feb 4, 2015 at 23:10
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An SSD's service life is rated in total write cycles and is very precise. A Traditional spinning hard drive's service life is rated in hours of runtime, and can only be estimated in a very general way. It's important to note that HDDs and SSDs wear differently.

The flash memory cells in an SSD have a hard limit to the number of erase/rewrite cycles they can tolerate before they die. This number is fixed and predictable, so it is very easy to determine how "healthy" an SSD is. SSDs employ wear leveling algorithms in their firmware to spread out that wear and extend the life of the device.

Spinning hard drives are a different story. The individual magnetic bits can be flipped back and forth an infinite number of times. Furthermore, the mechanical parts (head armature and spindle motor) are controlled by magnets as well so they do not physically make contact against each other. Hard drives wear from heat, humidity, vibration, shock, microscopic defects in the manufacturing process, etc.

Doing a full, long format of an SSD WILL degrade the drive and is unnecessary most of the time.

Doing a full, long format of a spinning hard drive will not degrade the hard drive per se. The wear comes from the heads thrashing about, not by flipping bits back and forth.

Long story short, no, there is no effective limit to the number of times you can format a traditional spinning hard drive -- at least nothing beyond simply using it for the same length of time.

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    TIL that a full format does not overwrite every sector on disk. Still, this looks like something that could have been a tiny edit to my answer. I've gone ahead and edited my answer accordingly. Also, it's noteworthy that the moving parts of HDDs do wear out, even if the sectors on the platter don't. An HDD wears out just like an SSD; it just wears out differently. To test this, sit a brand new HDD in a cool, dry place in an electrostatic bag for 20 years, and take a new HDD and run it for those same years. The disk that ran will have failed; the one in the bag won't. Thus, HDDs wear out.
    – allquixotic
    Feb 4, 2015 at 17:09
  • I have completely rewritten my answer due to the link that @Daniel B provided. Windows changed its behavior as of Vista. Apparently Windows DOES zero out the drive on a long format now.
    – Wes Sayeed
    Feb 4, 2015 at 22:07
  • Are manufacturing tolerances such that SSD cell cycle lifetime is a precise number? I always thought it was a conservative number and your device could vary significantly from that number.
    – Johnny
    Feb 4, 2015 at 23:45
  • @Johnny Your initial thought that it's a conservative number is usually correct. For example, although the write endurance of the Samsung 850 Pro is rated at 150 TB, Samsung internally has had many drives breach the 1 Petabyte barrier, with a handful of them reaching several (up to 8!!!!) petabytes, without significant signs of disk failure aside from a small handful of cells gracefully wearing out. It probably depends in some strange way on your typical workload, write patterns, temperature, whether the unit incurs shock damage (as in a laptop) or is in a sterilized environment, etc.
    – allquixotic
    Feb 21, 2015 at 4:40
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The mechanism that wears out in hard disk drives is that which moves the heads in and out, "seeking". Over time they lose their calibration. Note that this takes a LONG time these days (not once the case). I bet that if you were curious enough, you could find the number of seeks that a HD maker expects from their drives. A quick format, which is mostly on track 0, causes minimal motion and minimal wear.

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    A quick format, which is mostly on track 0... I think you're confusing how a floppy disk is formatted with how fixed disks are formatted.
    – I say Reinstate Monica
    Feb 4, 2015 at 19:20
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    A modern voice coil mechanical drive is not going to lose calibration by seeking. Old stepper motor drives did suffer from drift though.
    – Brian Knoblauch
    Feb 4, 2015 at 20:05

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