so I have a 1TB HDD, and here's my question:

Is it worth doing a hard format? Does it have any performance variance from say, quick formatting?

I understand the technical difference between the two: quick formatting just tells the drives that all the sectors are writable, and doesn't really delete any data... The drive just writes over existing sectors as and when needed, while a hard format will clean the HDD completely, and wipe all data, (write 0's everywhere I think).

  • 4
    What a "Full Format" does is OS dependent. On XP, it does a read-only sector check, it does not write zeroes to the drive. On Vista/7, a full format writes zeroes to the entire drive. Sources: MS KB 941961 and MS KB 302686. You'll have to check other operating systems to be sure of their behavior. – afrazier Aug 5 '11 at 18:51
  • @afrazier Thanks for that note, I have updated my answer to include that detail. Do note that the Vista/7 format utility still does a sector check during a full format. – Breakthrough Aug 5 '11 at 20:00

A full format does not just clean the partition table data, it also checks every sector on the disk surface for corrupted ones. This is primarily why it takes so much longer to perform then a quick format. A quick format just rewrites the partition tables.

From a performance standpoint, there is no difference. When the HDD writes a file to the disk, it just finds the next available "free sector", and overwrites whatever is there (regardless of whether or not it is a 0 or a 1). Think of it like this: a quick format just "deletes" all of the files, whereas a full format performs a sector check of the drive surface, and depending on the formatting utility, may fill the drive with zeroes (the default format utilities included with Windows do not zero-fill the drive. Most disk manufacturers provide diagnostic utilities which include the ability to do this.

If the drive is brand new, you should be fine with a quick format. If the drive has corrupted sectors (or even if you think that it does), it would be worth your time to do the full format. If you want to play it safe, ensure that you do at least one full format to the drive. That should reveal all bad sectors, and from then on, you can just do quick formats.

  • 4
    +1, didn't know that it did a sector check too! – Darth Android Aug 5 '11 at 18:40
  • Isn't reading sectors then same type of check as writing to them? – Moab Aug 5 '11 at 21:28
  • Oh.. Well, that's sad then... Shouldn't've wasted all night formatting that 1TB hdd then... :-( In either case, thanks for the answer... :-) – Abhishek Aug 8 '11 at 2:07
  • Quick correction: a (quick) format rewrites the file system metadata, including file tables and free space bitmaps. Partitioning is the act that writes partition tables, not formatting - formatting is applied to the partition, not the whole drive. Typically, from a clean drive, you initialise (write MBR/GPT), partition (write partition information into MBR/GPT partition tables, including an id/guid to identify the file system) and format (write file system metadata to the partition). – Bob Oct 25 '12 at 14:07


I use Western Digital's Data Lifeguard tool to zero fill drives, it will do any brand. Once it is done the drive becomes "unitialized" in disk management, back to a factory state. This leads me to believe it writes to sectors a format does not.

I use this on drives that have problems installing an OS to when there was a previous installation, solves all kinds of weird problems.

Choice of format has no effect on performance of a drive

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  • The only sectors that a vendor's tool writes to that a format doesn't are areas outside of the partitioned space, like the boot sector and partition table. – afrazier Aug 6 '11 at 0:08
  • 3
    diskpart has a clean command that will destroy the MBR/GPT (including partitioning information) and the first and last 1MB (equivalent to the WD quick erase). The drive will then come up as 'uninitialized'. If you use the optional all argument (i.e. clean all), it will fill the entire drive with zeros (equivalent to the WD full erase). For more information, run diskpart and enter the command help clean. Select the correct disk with list disk followed by select disk=#, but be very careful with which one. – Bob Oct 25 '12 at 14:02

As others have said doing a full format checks the entire disk, typically by writing data to it (all ones or all zeros) and then checking to make sure the written data is correct. If the data is not correct then an entry is made in a table that keeps track of bad sectors. I'm trying to be generic here because there are quite a few OSs. Since the format identified bad sectors, those sectors can never be written to since they were recorded in the appropriate table. They are never free sectors in other words. When someone says you only need to do a full format only once, I don't know how effective that is for disk integrity. As a disk gets older you are more likely, not less likely to have surface areas develop problems.

This is all about data security, and reading comments from others doesn't always = a safe system for YOU.

If you are wondering if a full format wipes the disk clean, in most OSs it does since it had to write data to read it back to ensure good sectors. I read another comment that a person looked at the data on the disk after doing a full format and sure enough the format data was left there, and in this case the format pattern is 00EE = in binary 0000 0000 1110 1110.

So if you are wondering about security of data that you are putting on the disk, doing a full format ensures that you don't write to a bad sector. Even though newer disks reserve some sectors in case others go bad (sectors that otherwise don't get written to), that still hasn't saved me in the past. I had a patch of bad sectors at the end of a disk, and of course I didn't know about it until the disk filled up. Once I started writing to that part of the disk I started getting write errors, and it would hang up my computer for a little bit. The disk couldn't recover from it and the data was lost. If I would have done a full format from the very beginning that wouldn't have happened. In fact, I would have sent the disk back and got another one, assuming the surface problem was there from the beginning (and I am).

If you are talking about security where you want to wipe out data so it can never be read, then there are different tools that can do that and some come bundled with software you might have such as virus protection/internet security software, or different disk tools that will do it. I think there are some free options for that, but if nothing else there are disk tools that are pretty cheap to buy that you can have for the rest of your life (as long as the tool is compatible with later OS's). I'd say that's better than doing a format for that purpose. Now, if you are simply trying to keep out an amateur from seeing the data that you used to have on a disk, then a full format in most OS's does the trick, but not all. Any that write data and leave that data when the format is done is good enough for that purpose.

I do a quick format pretty much all the time unless it's a smaller disk (2TB and less). You simply plan on doing something else for a while during the format. A full format though is not about zeroing out the disk; it's about writing a pattern and then checking that pattern to ensure that the surface is good and putting into a table any that aren't.

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