A few days ago a friend asked me what the difference was between performing a quick format and a regular format. First thing I should mention here is that we are talking about used drives, so ‘reformat’ is probably the more precise term. Anyway, technology is not my forte by any means but I relayed what I knew in layman’s terms which satisfied my friend, but also made me realize my own understanding of the processes was pretty limited. So I decided to research the subject and expand my knowledge in this area.
First thing I noticed; there is a heck of a lot of misunderstanding and misconception about what actually happens during a reformat; much of which can be attributed to changes Microsoft adopted for Vista. Pre Vista operating systems, including XP, handle the Quick Format in much the same manner but the Regular Format changed in Vista and those changes carried through to Windows 7.
Unfortunately, many sources are still quoting the older information relevant to XP, even though they are discussing Vista/Win7. This, of course, not only confuses the issue but also makes it pretty difficult to get a handle on. After much research, this is what I have come up with:
Quick Format:
Does not actually overwrite, delete or erase any existing data. A Quick Format simply creates a new master file table (MFT), which subsequently renders any existing data unreadable/inaccessible. The MFT lets the system know where files are on the disk, sort of like the index section of a book, because the new MFT doesn’t reference existing files they cannot be accessed. All the existing files are still there and can be quite easily resurrected using fairly basic data recovery software.
Regular Format:
Pre Vista: Is exactly the same as the Quick Format except it also checks the drive for any bad sectors (same as running chkdsk /r). Existing data is not overwritten or erased and the extra time involved is totally taken up by the disk checking function.
Vista & Windows 7: Actually performs a rewrite pass over the entire drive. This adds a level of security to the process and provides a cleaner starting point for fresh data.
*Please be aware that the Regular Format’s one pass rewrite is adequate for disks which are being retained/re-used but definitely not secure enough for disposal. If you are passing a hard drive on, you will need to use software which performs multiple rewrite passes in order to render the data pretty much unrecoverable. In fact, if you are discarding a hard drive altogether, then I would suggest smashing the heck out it with a hammer first…very secure and great fun too!!
Hi Jim – Thanks for that message.
I too have been using computers for decades, cutting my teeth as a system manager on DEC VAXes. I remember paying $14,000 for a 400 MB hard drive. However, that doesn’t make me an expert on anything that’s happenning today, given the current rate of technology change, and given that I’m sitting on a sailboat at anchor and am an ‘inadvertant luddite.’
I have, over the years, noticed that bad hard drives are almost a thing of the past, and have begun to suspect that once the HD manufacturers run them through a QA test to detect defects the odds of a sector going bad are pretty darn slim.
But (and this is the actual question) I wonder if the bad sector info survives a format change from FAT (or FAT32, or exFAT, or newFAT) to NTFS. I suspect it does, but don´t know.
I just picked up a 1TB USB drive for something like 2000 pesos, and you can imagine how long it takes to do a long format over a USB 2 bus. Since I live on a boat and live on 12 volts, that doesn´t do the batteries much good. Yet most external drives (I have five) ship with a FAT variation since there´s no telling what OS it will be installed on.
I´m just curious of you know anything about whether sector info survives a change of format type. I think there are only a hand full of actual manufacturers out there, and most drives regardless of brand are made by Seagate, Western Digital, Samsung, and a few others. I think they probably have worked with Microsoft and Apple to come up with a standard way to handle this. But, really, I have no idea.
Wal
Hey Wal – Interesting comments mate!!
“‘inadvertant luddite” – I like it!! Although owning 5 drives seems to be a contradiction. [grin]
As for your question: well, as I relayed in the article, technology is not exactly my forte. But this is what I understand:
I agree with your suspicion, bad sector info would definitely survive a change of format. Bad sectors actually reflect physical defects on the surface of the hard drive, they can’t be resurrected but they can be managed. That’s part of the reason HDD’s seem to last longer these days; modern drives constantly monitor data in both directions, data subsequently stored on a bad sector is redistributed and the bad sector then closed for business.
Dave is much better with this stuff than I, hopefully he may read through these comments and respond (although, I hope he doesn’t need to correct me) [smile]
I’ve always bought WD hard drives, only ever had one problem and that was with a very old drive. So I have tended to stick with the brand which has worked well for me.
Cheers mate…Jim
@Jim / @Wally — I have to disagree. Also a hunch. But my reasoning is, sure the physical defect will still be present on the drive regardless of what you change the defect too; but the drive itself doesn’t know about the defect, the defect was detected by software and saved in the FAT or in the Journal, etc… and when you erase the FAT table / Journal table, etc… the information about that bad sector is now gone. Now there may be additional layers of protection happening at the hardware layer, and such, and of course any of that error recovery information will persist, but a bad sector detected at the logical level — unless you’re going from the same format type to the same format type (i.e. reformat FAT32 as FAT32) — AND — the tool is smart enough to carry the information about the bad sectors over — then I would put my money on that information not persisting. Hence, if you re-format a drive with bad sectors — it’s a good idea to follow it up with a “chkdsk /R /X” (or equivalent) on the disk!