Hello everyone,
I just want to know what is a low level format??? Thanks

"A low-level format, or physical format, is the first process that must have been carried out to a new drive before it can be partitioned and high-level formatted. You cannot low-level format a drive with the FORMAT command and you must have either the correct utility for your drive or in-depth knowledge of the drive you are going to perform the low-level format on."

Low-level formatting isn't really something you need to do on a new drive today... it rewrites all the various formatting information onto each sector of the drive, and does more than simply overwrite it with 0s.

The only ~true~ low-level format is done at the manufacturers factory.

Not so.

Many OEM integrators and even vendors have hardware to do this.

Also, there are a few software utilities that can perform actual low-level formats. (Although I haven't actually seen one of these in about a decade.)

Not only that, but my motherboard actually features a low-level formatting utility in firmware.

In addition, most SCSI host adapters are *quite* capable of performing a low-level format.

Important drive information (servo, sector layout, and defect management, etc.) is stored in the low-level format at the factory. This information is designed to last the life of the drive and therefore it is not possible to low level the drive outside the factory. Although some drive manufactures and BIOS provided so-called "low level format utilities", they actually perform a write-read verify of the drive’s user data sectors, and do not actually perform a low-level format. Hitachi does not provide such utility.
In the event of a corrupted master boot record or boot block virus, use FDISK /MBR command to restore the master boot record. back
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http://www.pcguide.com/ref/hdd/geom/formatUtilities-c.html

Low-Level Format, Zero-Fill and Diagnostic Utilities

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.

Nice, comprehensive link, Dan.

I should have been more specific.

The point I was trying to get across is this:

It isn't true that only drive manufacturers can perform real low-level formats.

Dan's statement might as well be true as far as most modern drives and the vast majority of end users are concerned, but it is not correct. Many drives can (and sometimes need to be) be low-level formatted by someone other than the manufacturer and outside the factory. Also, some drives were never low-level formatted by the manufacturer to begin with.

As late as 1994, most drive manufacturers did NOT low-level format their drives. The drives shipped from the manufacturer's factory with the platters totally, utterly, completely blank. No defect maps, no sectoring, nothing. (There were good reasons for this practice.)

Low-level formatting was the responsibility of whoever bought the drive--usually manufacturers or vendors who built computers, but in some cases, end users. I still remember purchasing a hard disk from Seagate and having to personally give the drive it's first low-level format--and not with Seagate's software, either.

If you bought a system with a hard drive already installed by the manufacturer or dealer, a low-level format was probably already done for you, but these low-level formats were performed only after the drive had been installed in the system and at the expected physical orientation and operating temperature.

If you ordered a hard drive from the manufacturer, you had to perform the low-level yourself or get someone else to do it for you--after you installed the drive.

Of course, manufacturers DID supply the defect list.

Many computer system and hard drive manufacturers provided real low-level format utilities. IBM provided a low-level format utility for the PC/XT, the AT, and the PS/2 on the reference disks. (BTW, the PS/2 version was pretty slick; the PC/XT and AT version really bite.)

I have performed actual, "true", low-level formats on several of my own drives--this was often necessary. In some cases, it was necessary to make it compatible with a specific controller (some controllers didn't support some interleaves and some worked optimally for specific interleaves). Sometimes it was to cure tracking issues (damn open-loop voice coils!). Mostly, it was for defect management, though.

Of course, these drives I'm talking about are not ATA drives with RLL- and MFM-encoded disks made from about 1979 to 1983 and run in restored or hot-rodded IBM XT systems.

However, these were "true" low-level formats in every sense and they were certainly not done at the manufacturer's factory!

What Dan Penny (and a good bit of the PC Guide article) is talking about is confined to modern ATA and SCSI hard drives. In this context, the statement is essentially correct. However, some of this information applies only to modern hardware and not all drives. Not all drives have servo information, defect maps, skew factors, and other data stored on the drive. Roughly half the drives I own don't have this, although all my modern drives do.

I understand the distinction he's making between low-level format utilities and newer utilities that are quite incorrectly described as low-level formatters, although I completely failed to make such a distinction myself. Quite honestly, I'm not very familiar with these mis-named utilities and frankly don't know that much about them--although I have spent countless, tedious, long, loooooooooooooong hours using actual low-level formatting tools.

For most of my low-level formatting, I used the IBM-provided utilities for the PC/XT (sucks!), AT (sucks!), and PS/2 and software from Ontrack. All these utilities actually do real, honest-to-god, low-level formats.

The low-level formatting utility included with my motherboard appears to have also been a real low-level formatter, although I don't know this for a fact. The utility required the typical data to be entered--interleave, skew factor, defects, etc.--and took a godawful long time to run. (The motherboard is a Tyan Trinity 100 AT model s1590s (pre-revision). If anyone has addition info about the low-level formatter originally included with this board, let me know. Note: This utility was *only* available in the original version of the board (which supported 256MB DIMMs) and with the original BIOS. The utility was *promptly* removed after the board was introduced, no doubt because many people screwed up their hard drives playing with it.)

As for the low-level formatting utility included with the SCSI host adapters are true register-level low-level formatting utilities. With SCSI, the interface to the drive is though the host adapter, so this stuff is not hard drive-specific. In other words, the low-level formatting utility has to be custom tailerd for the SCSI host adapter--not the hard drive. (Yet another reason I'm a SCSI fan.)

It's not categorically true that only the manufacturer can perform a true low-level format. For modern drives, this is indeed the case, but not for many older drives. This may seem like hair-splitting, but I've seen more than a few posts on Computing.Net forums regarding the old stuff--particularly in the DOS and Windows 3.1 forums and many sites devoted to old hardware. Maybe these people are hopelessly insane, perverts, or some sort of nouveaux luddites--I couldn't say, but there's quite a culture devoted to vintage hardware and software and for them, the statement couldn't be further from the truth.

I wouldn't have even bothered posting anything on this thread had this been in the Windows XP, BeOS, or some other forum where people are practically guaranteed to never, ever, ever have to low-level format drives. If you're working with older gear, though, it's not only possible to perform real low-level formats, sometimes it's downright necessary!

Speaking of low-level formatting software (*real* low-level formatting utilities, not this zero-fill stuff)...

If you're low-level formatting a standard PC/XT hard drive (8-bit XT interface, ST-506/412 controller, etc.), I don't recommend using the low-level utility supplied by IBM. It can actually render many IBM XT drives useless and really is just absolutely awful.

The PC/XT low-level format utility from IBM only allows a 6:1 interleave--but most disk controllers in PC/XT systems are designed for interleaves between 2:1 and 5:1! Who knows why this weird mismatch between the OEM software and hardware occurred, but there you have it. Using the IBM utility can lead to a very, very slow XT. I once got an XT with all original factory hardware but a remarkably slow hard drive. I am convinced this is because the drive was low-levelled with the IBM utility. After low-levelling with a 1:3 interleave, it ran great.

Another insane problem with PC/XT low-level format utility is that it doesn't let you enter the defect list! (What the hell were they thinking?)

The AT version of this utility cannot handle a 1:1 interleave. If your controller can't handle anything other than a 1:1 interleave, this is a problem.

The PS/2 low-level formatter is much better and I recommend using it.

For ATA hardware, the Ontrack Disk Manager is *excellent*. It's a true register-level low-leveller than goes around the BIOS and manipulates the hardware directly. It can handle vendor-specific code, tell when ECC has been used and can even manipulate ECC bytes.

MicroScope works great too.

If you're serious, stay away from anything that relies on BIOS software interrupt services. These INT routines do a lot of abstraction and mask a lot of s---.

Utilities that use the CCB interface are recommended--assuming the hardware support CCB commands--all modern drives and most drives made since 1984 do.

By the way Dan, thanks for the information about the so-called low-level formatters that just wipe the data areas of the disk. I didn't realize these existed. Some real low-level formatters give the option of doing a zero-fill without performing a complete low-level format, but I wasn't aware that some utilities billed as low-levellers can ONLY perform this function.

For those of you who wish a more simple explanation, I am going to over simplify: A high level (normal) format does not erase the bad section flags and some other "system" data where as a low level format erases and rewrites everything.
Therefore, from this vantage point running IBM WIPE.COM on a drive and then following it with a thorough SCANDISK surface scan is a poor man's low level format.
Another thought on WIPE.COM: Because you can use it at all without wiping out a drive, data like interleve ratio must be hard coded into the drive hardware in modern drives. You don't have to worry about it in any case. (But you will erase the data that tells software the size of the drive when you use wipe. This only becomes inconvenient when you use drive detection software utilities)