Why Low Level Format?

The only time you might need a low level format is when the partition tables or something else is so messed up that a regular format won't complete.

A low level format bassicly writes "0"s to every sector of the disk including boot sectors. This places the drive in a state like it just came from the factory.

When you do a regular format, the bad sector list is kept. Every drive has a few extra sectors. When it finds a bad one, it marks it as not usable and uses a spare sector in its place. A low level format removes this as well.

Generally, you don't need to do one. If you are getting rid of the drive and are worried about someone getting the contents of the disk, using something like Autoclave instead. It will do a much better job.
 
Actually, from what I remember from one of the zillion threads we have about this every now and then, you can't do a low level on current drives. It can only be done at the factory. You can zero out a drive, but that's not really a format.

Correct me if I'm wrong, but I seem to recall that IDE drives can't be low leveled by the consumer.
 
You can think of it like a highway. A regular format just gets all the cars off the road. A low level format also tears up the road.

Hard drive platters are rarely perfect. They have defects and the hard drive has a space set aside with a map of these defect areas. A low level format effectively destroys this list so you need to reinput the values. So to use the highway example, when you low level format, you among other things explain where the impassable terrain is so the road crew doesn't try to put road there.

Low level formatting was used more several years ago.. SCSI drives in the early 90's were especially picky about what controller they were used with, and it was common practice when taking a SCSI drive from a controller of one brand to a different brand, to do a low level format. Back then hard drives also had the bad sector map plainly displayed on the drive label showing the bad sectors from the factory, with adequate blank space for writing in more values as the drive degraded.

These days, if you have an absolute need to do a low level format, in most cases it's a sign the drive is dying and should be replaced.
 
You can change the sector size when you reformat. Some exotic
systems (Clariion RAID arrays are a famous example) use a
weird sector size.
The tearing-up-the-highway example is very good. Reformating
actually lays out where the tracks & sectors go, so it's just
like building a new road.
 
XOR != OR said:
Actually, from what I remember from one of the zillion threads we have about this every now and then, you can't do a low level on current drives. It can only be done at the factory. You can zero out a drive, but that's not really a format.

Correct me if I'm wrong, but I seem to recall that IDE drives can't be low leveled by the consumer.
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You would be correct in this. Low Level Formatting can only be done by drive OEMs. It's a phrase that stuck to "zero-filling" the drives, because it doesn't more than just deleting the partitions. It's a "lower level", but not the same as low level formatting.

The funny thing is, like many other points these boards....despite the fact that it's corrent, known, accepted, and factual, some people will come along and try to argue with you anyway.
 
Lowlevel formatting
Low-level formatting is the process of outlining the positions of the tracks and sectors on the hard disk, and writing the control structures that define where the tracks and sectors are. This is often called a "true" formatting operation, because it really creates the physical format that defines where the data is stored on the disk. The first time that a low-level format ("LLF") is performed on a hard disk, the disk's platters start out empty. That's the last time the platters will be empty for the life of the drive. If an LLF is done on a disk with data on it already, the data is permanently erased (save heroic data recovery measures which are sometimes possible).

If you've explored other areas of this material describing hard disks, you have learned that modern hard disks are much more precisely designed and built, and much more complicated than older disks. Older disks had the same number of sectors per track, and did not use dedicated controllers. It was necessary for the external controller to do the low-level format, and quite easy to describe the geometry of the drive to the controller so it could do the LLF. Newer disks use many complex internal structures, including zoned bit recording to put more sectors on the outer tracks than the inner ones, and embedded servo data to control the head actuator. They also transparently map out bad sectors. Due to this complexity, all modern hard disks are low-level formatted at the factory for the life of the drive. There's no way for the PC to do an LLF on a modern IDE/ATA or SCSI hard disk, and there's no reason to try to do so.

Older drives needed to be re-low-level-formatted occasionally because of the thermal expansion problems associated with using stepper motor actuators. Over time, the tracks on the platters would move relative to where the heads expected them to be, and errors would result. These could be corrected by doing a low-level format, rewriting the tracks in the new positions that the stepper motor moved the heads to. This is totally unnecessary with modern voice-coil-actuated hard disks.

Warning: You should never attempt to do a low-level format on an IDE/ATA or SCSI hard disk. Do not try to use BIOS-based low-level formatting tools on these newer drives. It's unlikely that you will damage anything if you try to do this (since the drive controller is programmed to ignore any such LLF attempts), but at best you will be wasting your time. A modern disk can usually be restored to "like-new" condition by using a zero-fill utility.
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Its impossible to do a true lowlevel format on a modern drive outside the factory do to the distributed servo bursts, the increased areal density ect

per request Im now including intermissions with my longer posts :p

Zero Fill
Older hard disks required periodic low-level formatting by the system configurator or end-user. To facilitate this, low-level format utilities were created. These are small programs written to control the low-level formatting process for the hard disk. The hard disk controller would normally include one of these programs in a ROM chip in hardware, enabling access to the software without requiring any drives to be running in the system, and thus avoiding a possible "chicken and egg" quandary. In addition, more sophisticated, third-party utilities were available that would perform an LLF and also do other related features such as scanning for bad sectors or analyzing the drive to determine an optimal interleave setting. These would typically be loaded from a floppy disk.

Low-level formatting an older hard disk could be a rather complicated procedure, particularly for one who was not very familiar with PCs and hard disks. Various factors needed to be taken into account, such as defect mapping and setting the interleave factor. The particular conditions of the drive when formatting were also important: due to the vagaries of stepper-motor actuators, doing an LLF when the drive was very cold or very hot could lead to errors when the drive returned to a more normal temperature. Even the orientation of the drive when it was formatted was an issue.

As I have said (probably too often, sorry) modern drives do not need to be low-level formatted by the end user, and in fact cannot be LLFed outside the factory due to their precision and complexity. However, it seems that the need to LLF hard disks on the part of users has never gone away. Like some primordial instinct, many PC users seem to have a fundamental desire to LLF their modern disks. Maybe it is built into the genetic code in some way yet undiscovered. ;^) In fact, even if it were possible, the vast majority of the time that someone "needs" to LLF a hard disk today, it is not really necessary. Many users jump quickly to wanting to try an "LLF" whenever they have a problem with their hard disk, much the way many jump to re-installing their operating system whenever it gives them trouble.

Hard drive manufacturers have created for modern drives replacements for the old LLF utilities. They cause some confusion, because they are often still called "low-level format" utilities. The name is incorrect because, again, no utility that a user can run on a PC can LLF a modern drive. A more proper name for this sort of program is a zero-fill and diagnostic utility. This software does work on the drive at a low level, usually including the following functions (and perhaps others):

* Drive Recognition Test: Lets you test to see if the software can "see" the drive. This is the first step in ensuring that the drive is properly installed and connected.
* Display Drive Details: Tells you detailed information about the drive, such as its exact model number, firmware revision level, date of manufacture, etc.
* Test For Errors: Analyzes the entire surface of the hard disk, looking for problem areas (bad sectors) and instructing the integrated drive controller to remap them.
* Zero-Fill: Wipes off all data on the drive by filling every sector with zeroes. Normally a test for errors (as above) is done at the same time.

When most users today talk about "low-level formatting" a drive, what they are really talking about is doing a zero-fill. That procedure will restore a functional drive (that is, one that does not have mechanical problems) to the condition it was in when received from the factory. There are occasions when a modern hard disk can become so badly corrupted that the operating system cannot recover it, and a zero-fill can help in this situation. Stubborn boot sector viruses for example can be hard to eradicate without resorting to low-level intervention. Since the zero-fill cleans all programs and data off the drive it will get rid of almost any data-related problem on the drive, such as viruses, corrupted partitions and the like. Just remember that it's a bit like burning down your house to get rid of termites: you lose everything on the drive.

This type of utility can also be used to "hide" bad sectors by telling the drive to remap them to its collection of spares. Just remember that a drive that continues to "grow" bad sectors over time is one whose reliability is highly suspect. I discuss this matter in more detail here.

Warning: Only use a low-level zero-fill or diagnostic utility designed for your particular hard disk. You can download one for free from your drive manufacturer's web site. Even though damage probably won't result from using the wrong program, you may lose data and you may also complicate any warranty service you try to have performed on the drive. (Technical support people at "Company X" generally don't like to hear that you used a utility on their drive written by "Company Y".)

Warning: Always back up your data before you use a low-level utility, and make sure that you carefully follow all of the instructions provided.

Warning: Never run a low-level disk utility from within a multi-tasking operating system such as Windows 9x. Other programs running in the background could interfere with the utility. Restart the computer in MS-DOS mode first, or reboot the computer from a floppy.
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a zero fill is slightly more useful than made out above and has on many occassions sorted out issues that arent fixable any other way, getting rid of Dynamic Drive Overlays for instance (though it can sometimes fail at that) or just another chance to lock out bad sectors
 
djnes said:
The funny thing is, like many other points these boards....despite the fact that it's correct, known, accepted, and factual, some people will come along and try to argue with you anyway.
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AlexStenka said:
What about killdisk I just used it and low loveled formated
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Guess that proves your point (djnes') :p
 
djnes said:
The funny thing is, like many other points these boards....despite the fact that it's corrent, known, accepted, and factual, some people will come along and try to argue with you anyway.
Click to expand...

or at least until I come along and uncork the information overload :p
 
I can do low-level formatting on a floppy. With a magnet. You won't tell the difference between a new factory-sealed floppy, or a MAC-formatted floppy, for that matter.

Ice Czar doesn't know much about RAM, so he moved over to this forum to insult our intelligence. Bah, I say, bah! ;)
 
Worried about someone getting your data? Smash your hard drive into a million pieces. Quick, easy, and fun! :D
 
The magnet trick works, though.

Edit: Don't do it on credit cards.
 
valkyre said:
Worried about someone getting your data? Smash your hard drive into a million pieces. Quick, easy, and fun! :D
Click to expand...

That's definitely going to make your data safe from prying eyes!
 
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