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Every couple of months I find my computer becomes sluggish, so I format the hard drive then reinstall Windows to keep it running fast. I've been doing this for about a year without any adverse effects; but then, I was chatting to someone and they told me that formatting this often can damage the hard drive.

Is this true?

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That is a terrible thing to do. I dont think that you will damage the HD that way, but its a very silly (putting it lightly) way to maintain an OS. –  soandos Jun 14 '11 at 1:47
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@soandos, for a nice clean slate (though technically, all of the clusters already contain stuff, even if they are marked as unused). –  Synetech Jun 14 '11 at 3:08
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I assume its a magnetic drive. An SSD drive has a much lower number of write cycles, and so many formats, reinstalls, and updates would add a bunch of writes. –  Rich Homolka Jun 14 '11 at 3:13
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Actually, [1] formatting the system [2] installing everything, [3] update everything, then [4] image system... When you need a format, try [5] backup data, [6] restore image and [7] update everything.. at least sounds better than a full wipe every time.. anyways... –  bubu Jun 14 '11 at 9:11
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Have you heard of ghosting software? Norton Ghost is a well known one that I have used a lot in the past - this would save you hours! Each time you re-ghost, download updates and create a new ghost image. –  Matt Wilko Jun 14 '11 at 13:08
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up vote 29 down vote accepted

Formatting a drive is simply a matter of rearranging the bits, which is functionally no different from reading and writing files. I do agree with @soandos in that it is not a great way to maintain your OS, but it won't harm your drive, or reduce it's life significantly.

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Yup, if writing to the drive were harmful, the drive wouldn’t be very useful. I wonder if that person was thinking of something different than normal formatting, like “low-level formatting” or something, although even then… –  Synetech Jun 14 '11 at 3:09
    
I've heard this argument from people before ... hearing it since I was using 5.25" floppy diskettes. –  Kirk Jun 14 '11 at 3:13
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To be fair, 5¼" floppies (and 3½") really did have limited life and would in fact wear out after a while. –  Synetech Jun 14 '11 at 3:15
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It would shorten the life of an SSD drive though, wouldn't it? –  Svish Jun 14 '11 at 6:50
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@Svish only if you do a "full format" i.e. set all the bits in the drive to zero. If you only delete the file table (aka "quick format") it isn't more damaging to the SSD than deleting a large file. –  dtech Jun 14 '11 at 9:54
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Hard drives are good for hundreds of thousands of write cycles, if not millions. Even the early generations of SSDs are good for a few thousand write cycles.

When quick-formatting your drive you are just rewriting the first few sectors once, and when reinstalling your OS you are writing a couple of gigabytes of data once, with a few sectors possibly being written to a few dozen times.

Multiply a few dozen writes by 4 times or so per year, and you are still nowhere near to causing any significant wear on the key sectors of the drive.

Memory paging (which is enabled by default in most installations) causes more wear to your drive in one day (by repeatedly writing to the same sectors) than you would in years of formatting with the frequency you described.

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Good point about SSDs; perhaps that person was thinking of them and considers the OA’s behavior to be wasted/unnecessary writes that could be “saved/horded” for more useful purposes. –  Synetech Jun 14 '11 at 3:11
    
Why does repeatedly writing to the same sectors cause more damage? –  Maxpm Jun 15 '11 at 0:27
    
It actually does not if the controller in your SSD does wear leveling: it is free to change the mapping between sectors your operating system can see and actual pages on the flash memory, in a way that spreads write across the whole drive as best as possible. –  danielkza Jun 21 '11 at 23:37
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No.

Formatting your hard drive does not involve doing anything mechanically different compared to reading or writing to disk.

One way a drive could 'wear out' faster is if the operating system was doing a lot of memory caching to disk, also known as 'disk thrashing'. Another way is if your filesystem was heavily fragmented, and the disk had to traverse large sections of the hard drive platters to fetch data.

Formatting does not fall under any of the two above scenarios.

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One additional thing a low level format does is add bad sectors to the bad sector list. As others have said this is killing a fly with a hand grenade. If you have enough bad sectors to slow down Windows, get a new drive.

Also, so many installs may make you sloppy when it comes to updating the OS or apps, making you more likely to get malware.

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@Rich How would I go about checking this? –  aligray Jun 14 '11 at 3:12
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A disk scan. In Windows you would use the command chkdsk /f /r –  Synetech Jun 14 '11 at 3:13
    
@Synetech Inc. Is this in the event log as well? –  Rich Homolka Jun 14 '11 at 3:15
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Is what in the Event Log? The list of bad sectors? No, though a copy of the output from chkdsk is copied to the Application event-log (under the Winlogon source), but only for scans run at boot time, not after logging in. –  Synetech Jun 14 '11 at 3:18
    
@Synetech - You can also grab an Ubuntu disk and run it in "Live" mode (runs from the CD/DVD). Ubuntu has a disk monitoring program that monitors by default (in Ubuntu versions 10.04 or later). In my experience, it's the most sensitive, and accurate, at picking up bad sectors (and it will let you know right away if a drive has gone beyond a certain threshold of bad sectors). It also gives you a good breakdown of your drive's status. –  Shauna Jun 14 '11 at 12:10
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Technically, any use of a drive shortens the MTBF (Mean Time Before Failure, I think). But, as someone said, nowadays that's a huge number. Drives aren't guaranteed beyond that. But they will all eventually fail with use from simple wear and tear; they have moving parts and spin platters at incredible speeds and high temperature.

Low level formats aren't possible on new drives; bad sectors are mapped out by the firmware. Each cylinder of a disk has extra sector(s), and when a sector begins to fail, it is moved to the fresh sector and re-mapped. When the extra space on one cyl fills up (drive is really going bad) it borrows the next cyl's space. I'm not sure what that means to the defragment programs, but I assume they handle it properly or are completely blind to it.

I agree that formatting is no more damaging than any other function. Less than my StarCraft II game, by far!

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