hleaves@ruby.vcu.edu (EAVES,HUGH) (01/17/91)
I have a few questions about formatting disks. Any responses would be appreciated... 1. What is a low-level format? What does it do? (that is not done by a high-level format) 2. What is a high-level format? What does it do? 3. Are hard disks formatted differently than floppy disks? (is a floppy formatted at a low-level, where as a hard disk is formatted at a high-level?) 4. I understand that the MS-DOS format command only performs a high-level format of hard disks. Does it do the same thing for floppy disks? Thanks in advance, Hugh ******************************************************************************* ** Hugh L. Eaves ** Internet: hleaves@ruby.vcu.edu ** ** Medical College of Virginia ** Bitnet: hleaves@vcuruby ** ** Department of Human Genetics ** Voice: (804) 371-8754 ** ***************** All non-incendiary communication welcome! *******************
mahrk@ccicpg.UUCP (MHR {who?}) (01/18/91)
In <61737@brunix.UUCP>, hleaves@ruby.vcu.edu writes: > I have a few questions about formatting disks. Any responses would be > appreciated... > > 1. What is a low-level format? What does it do? (that is not done by a > high-level format) > An unformatted disk contains no flux changes on it, and hence no information which has any meaning. A low-level format writes sector information on the disk so that it can be read and written by the driving software in a meaningful fashion. This also usually destroys any other information which may have previously been recorded on the disk. > 2. What is a high-level format? What does it do? > In MS-DOS (only), this is the second stage formatting done on hard disks which divides up a (previously low-level formatted and FDISK'd) partition of the disk into the peculiar arrangement MS-DOS uses for its information. > 3. Are hard disks formatted differently than floppy disks? (is a floppy > formatted at a low-level, where as a hard disk is formatted at a high-level?) > Yes and no, in that order. Hard disks are formatted at the low level by either the factory, a piece of code contained in your disk controller's BIOS or the ROM-BIOS (for dumb controllers), or a smart formatting program for your disk, or some combination thereof. Then you have to run FDISK to partition the disk, and how many and what size depend on your version of MS-DOS and other disk support software you may have. Then the FORMAT program does the high-level format on the disk. For floppy disks, the FORMAT program does both the low and high level formats at the same time (more or less). > 4. I understand that the MS-DOS format command only performs a high-level > format of hard disks. Does it do the same thing for floppy disks? > See #3. > Thanks in advance, > Hugh > You're welcome. If I made any significant mistakes or misstatements here, corrections are welcome. If you want to be picky, use email please. -- Mark A. Hull-Richter UUCP: ccicpg!mahrk Clever remark stolen from ICL North America InterNet: [coming soon] another netter: 9801 Muirlands Blvd Go ahead, flame me. I have Irvine, CA 92713 (714)458-7282x4539 a /dev/null on my machine.
cgordon@vpnet.chi.il.us (gordon hlavenka) (01/21/91)
I am curious as to some of the details of the MS-DOS "High-level" format. If the LL format writes sectors, gaps, etc. and the HL format "builds the file system structures", why does the DOS HL format not complete in only a few sec- onds? DOS accesses the disk in clusters of (typically) 4 sectors per cluster. The DOS file system "structures" for a blank (but formatted) disk take up only a few sectors: 0 (boot sector), two FATs (approx 30-50 sectors/FAT), and a root directory (one cluster). Yet a DOS HL format takes several minutes and appears to make some kind of access to every sector on the disk. Is there some special "DOS Sector Header" which gets added? I know that DOS will mark clusters containing bad sectors during a format, so there is at least some kind of surface validation going on. Is this the only reason for access- ing the whole disk? Norton 4.5 has a "Quick Format" which only writes new FAT/root directory data. Is there any reason why this couldn't be used to install the DOS file system on a (non-bootable) LL-formatted hard drive? -- ----------------------------------------------------- Gordon S. Hlavenka cgordon@vpnet.chi.il.us Disclaimer: Yeah, I said it. So what?
yawei@bronze.ucs.indiana.edu (mr. yawei) (01/22/91)
In article <1991Jan21.022114.23765@vpnet.chi.il.us> cgordon@vpnet.chi.il.us (gordon hlavenka) writes: >I am curious as to some of the details of the MS-DOS "High-level" format. If >the LL format writes sectors, gaps, etc. and the HL format "builds the file >system structures", why does the DOS HL format not complete in only a few sec- >onds? As far as I know, MS-DOS was just reading through all the sectors to see that they are okay. Of course hard disk reformatting is not something you do everyday, so one should be able to stand a little delay there rather than finding bad sectors later on. Some OEM's MS-DOS (don't remember who) actually *writes* to every sector. This also destroys whatever is there. Baring that, a high-level format is usually recoverable with the right software. yawei