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What is the difference between a regular Format and a Low Level Format?
What is the difference between a regular Format and a Low Level Format?
I have a program to do Low Level Formats. I had a flash drive that somehow got screwed up. A regular format did not fix it, but a low level format got it working again. |
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What is the difference between a regular Format and a Low Level Format?
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What is the difference between a regular Format and a Low LevelFormat?
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What is the difference between a regular Format and a Low Level Format?
In message , Paul
writes wrote: What is the difference between a regular Format and a Low Level Format? I have a program to do Low Level Formats. I had a flash drive that somehow got screwed up. A regular format did not fix it, but a low level format got it working again. A partition "Quick Format" assigns a file system to a partition. It has nothing to do with the workings of the disk drive itself. A Quick Format writes a FAT or $MFT, writes a file system header, and that's it. It doesn't check anything. A partition "Format" without the quick, does a read verify of every cluster after the same steps as the previous paragraph. If bad clusters are found, they're added to the $BADCLUS list. The intention is, with a regular format, to "block" any bad sectors so they cannot be used. A bad sector is defined as a sector returning a CRC error, where the automatic sparing can no longer repair it and keep the sector in service. ******* A "low level" format is a disk drive technology, It has nothing to do with partitions or even OSes. It's something that happens at the platter level. Modern drives have a servo pattern recorded at the factory. The drive is only allowed to write to data sector areas. So all that a modern drive can do, is "zero" out the data. It's not allowed to change any other aspects of data content. As a result, there is no "low level" format on a modern drive. Even if a command existed in the ATA/ATAPI command set for it, only the data sector portion could be written. On an "old" drive, both the sector head and sector data areas are candidates for writes. During a normal write operation, only the sector data is written. During a "low level" format, both the sector head and the sector data are refreshed. And back in those days, if you interrupted the "low level" format, the disk tended to be ruined. When really you should have been able to start the process over again. It suggests at the end of the low level format, some info must have been written to the "critical data" section of the platter at "track -1". That's also the area where the drive firmware is kept (when you flash a drive, track -1 gets the information stored there). A "low level" format can be beneficial to a flaky "old" drive, but you must not interrupt the process - even if the software looks like it's frozen :-/ Been there, and done that. Paul In the past few years, I've collected a load old/ancient disks, and used some of them to 'keep my hand in' doing XP installs on an old clunker PC. [These never seem to go the same way twice, but that's another story.] X-GSmartControl (and other tests) shows that quite a lot of these disks have a few minor historical errors, so I decided that it might be a good idea to do a low-level format on some of them (using HDD LLF Low Level Format Tool). This didn't seem to do any harm to the disks, but on one type (IIRC, all 160GB Seagate), when I tried to install XP, when it got to removing the installation disk and rebooting, the reboot came up with a blue screen showing the message "Unmountable boot volume" (and a lot more). IIRC, three Seagate disks did the exactly the same, but a couple of others (Maxtor 40GB, I think) were OK. So is this just a coincidence, or can a low-level format leave at least certain types of hard drives looking apparently OK - but unusable for installing an operating system on? -- Ian |
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What is the difference between a regular Format and a Low LevelFormat?
Ian Jackson wrote:
In the past few years, I've collected a load old/ancient disks, and used some of them to 'keep my hand in' doing XP installs on an old clunker PC. [These never seem to go the same way twice, but that's another story.] X-GSmartControl (and other tests) shows that quite a lot of these disks have a few minor historical errors, so I decided that it might be a good idea to do a low-level format on some of them (using HDD LLF Low Level Format Tool). This didn't seem to do any harm to the disks, but on one type (IIRC, all 160GB Seagate), when I tried to install XP, when it got to removing the installation disk and rebooting, the reboot came up with a blue screen showing the message "Unmountable boot volume" (and a lot more). IIRC, three Seagate disks did the exactly the same, but a couple of others (Maxtor 40GB, I think) were OK. So is this just a coincidence, or can a low-level format leave at least certain types of hard drives looking apparently OK - but unusable for installing an operating system on? That sounds like a 48 bit LBA problem (cuts in at 137GB, 120GB drives OK, 160GB IDE drives could deliver a surprise). That's a problem on IDE drives, before ATA/ATAPI 6 or so. Seagate offered a document on the topic, which is a place to start, but not the end of the story. Some of the pronouncements in here are overly pessimistic. http://web.archive.org/web/200701210...c/tp/137gb.pdf Older IDE hardware, before 2003, supports 28-bit LBA, and that causes a limitation in practical partition size. If the address rolls over in hardware, an attempt to write to the 137GB mark, ends up writing to location zero, wiping out the file system header or other valuable goods. After 2003, more BIOS and hardwares were claimed to support 48-bit LBA, which significantly extends the address space. There was an announcement by one of the motherboard companies, that all their stuff supported 48-bit on IDE, after a certain magic date. I think it was 2003, but my memory isn't very good. The original proposal to the standards body, on how to do this, is documented here (the year 2004 is the first time Archive.org took a snapshot). It was a "double-pumping" of some registers, to cause fewer interface changes or something. On page two, it shows how an extended set of information, is loaded, via the pattern in the upper table. That's how they fit 48-bits. https://web.archive.org/web/20041024...l/e00101r6.pdf I thought the behavior of Windows handled this pretty well. I'm surprised the boot was a problem. For example, Win2K SP2 won't make a partition larger than 137GB on a 160GB disk, so it won't get into trouble. (That's because Win2K SP2 can also corrupt a larger hard drive, given a chance. Win2K SP2 was doing the best job it knew how to do.) But if a second partition happens to span the 137GB mark, that could easily cause corruption. You can "import" a drive from a more modern OS, and have it ruined by Win2K SP2 (SP4 is OK). x 137GB ------------------------------------------------------------- Partition below 137GB Partition spanning 137GB = trouble is OK and works by itself | | ^ | A write to 137GB, goes down to zero, +-------------------------------+ corrupting the first partition or MBR ******* Using another OS drive, boot the system and do your forensics on the 160GB drives that aren't behaving themselves. It could be that the OS partition is completely trashed. See if you can spot the "NTFS" string in the first sector of the partition for example. A copy of HXD could help, as it has an option to open a hard drive for low-level access. You will have to take your best shot at the math to work out where the partition(s) start and end. I like PTEDIT32 for this purpose - it's a great help, and it was easily available up until a year or two ago. https://mh-nexus.de/en/hxd/ ******* If you want to "cheat death" and you have the time to spend, try pre-formatting the 160GB drive. Say, make a 100GB partition and format it NTFS. Now, put it in the system where you'll be doing the install. Tell the installer to install in the 100GB partition (not above that). When you boot, it should work. Don't allow the installer to pick its own size (it indeed, that's how this mess was caused). Maybe you were using a WinXP Gold year 2002 or so CD ? Paul |
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What is the difference between a regular Format and a Low Level Format?
In message , Paul
writes Ian Jackson wrote: So is this just a coincidence, or can a low-level format leave at least certain types of hard drives looking apparently OK - but unusable for installing an operating system on? That sounds like a 48 bit LBA problem (cuts in at 137GB, 120GB drives OK, 160GB IDE drives could deliver a surprise). That's a problem on IDE drives, before ATA/ATAPI 6 or so. Seagate offered a document on the topic, which is a place to start, but not the end of the story. Some of the pronouncements in here are overly pessimistic. http://web.archive.org/web/200701210...te.com/support /kb/disc/tp/137gb.pdf Older IDE hardware, before 2003, supports 28-bit LBA, and that causes a limitation in practical partition size. If the address rolls over in hardware, an attempt to write to the 137GB mark, ends up writing to location zero, wiping out the file system header or other valuable goods. After 2003, more BIOS and hardwares were claimed to support 48-bit LBA, which significantly extends the address space. There was an announcement by one of the motherboard companies, that all their stuff supported 48-bit on IDE, after a certain magic date. I think it was 2003, but my memory isn't very good. The original proposal to the standards body, on how to do this, is documented here (the year 2004 is the first time Archive.org took a snapshot). It was a "double-pumping" of some registers, to cause fewer interface changes or something. On page two, it shows how an extended set of information, is loaded, via the pattern in the upper table. That's how they fit 48-bits. https://web.archive.org/web/20041024...10.org:80/t13/ technical/e00101r6.pdf I thought the behavior of Windows handled this pretty well. I'm surprised the boot was a problem. For example, Win2K SP2 won't make a partition larger than 137GB on a 160GB disk, so it won't get into trouble. (That's because Win2K SP2 can also corrupt a larger hard drive, given a chance. Win2K SP2 was doing the best job it knew how to do.) But if a second partition happens to span the 137GB mark, that could easily cause corruption. You can "import" a drive from a more modern OS, and have it ruined by Win2K SP2 (SP4 is OK). x 137GB ------------------------------------------------------------- Partition below 137GB Partition spanning 137GB = trouble is OK and works by itself | | ^ | A write to 137GB, goes down to zero, +-------------------------------+ corrupting the first partition or MBR ******* Using another OS drive, boot the system and do your forensics on the 160GB drives that aren't behaving themselves. It could be that the OS partition is completely trashed. See if you can spot the "NTFS" string in the first sector of the partition for example. A copy of HXD could help, as it has an option to open a hard drive for low-level access. You will have to take your best shot at the math to work out where the partition(s) start and end. I like PTEDIT32 for this purpose - it's a great help, and it was easily available up until a year or two ago. https://mh-nexus.de/en/hxd/ ******* If you want to "cheat death" and you have the time to spend, try pre-formatting the 160GB drive. Say, make a 100GB partition and format it NTFS. Now, put it in the system where you'll be doing the install. Tell the installer to install in the 100GB partition (not above that). When you boot, it should work. Don't allow the installer to pick its own size (it indeed, that's how this mess was caused). Maybe you were using a WinXP Gold year 2002 or so CD ? Paul Thanks for the comprehensive follow-up. I'm looking into the 137GB limit. The PC has an Asus motherboard (can't remember the model at the moment), and dates from 2001 or 2. The OS is XP Home, and I see that XP Home Service Pack 1 (SP1) or higher should be OK with 137G. [I've also tried a different installation disk which includes SP2, and had the same problem.] As the installation disk includes SP1, am I right to assume that this all gets installed before the reboot? If not, and only the basic XP gets installed initially, that might explain the problem. [It's quite some time since I did this (I see that I already raised the problem in January - but didn't go into as much detail about the disk sizes), so I can't remember if you replace the same disk after the reboot.] However, as you suggest, I'll try splitting the 160GB drive so that the first partition is less than 137GB, and see if that will accept an installation. I can also try cloning the present 137GB disk (it's either 40 or 80GB) to the 160GB disk (although I have a feeling that I've already tried that, but can't remember what happened). -- Ian |
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What is the difference between a regular Format and a Low Level Format?
In message , Ian Jackson
writes In message , Paul writes Ian Jackson wrote: However, as you suggest, I'll try splitting the 160GB drive so that the first partition is less than 137GB, and see if that will accept an installation. I can also try cloning the present 137GB disk (it's either 40 or 80GB) to the 160GB disk (although I have a feeling that I've already tried that, but can't remember what happened). Just an addendum..... I think I've already installed XP Home and XP Pro on several disks that were 160GB (and even more) - and also cloned to them. I therefore feel it's unlikely that the problem is a possible 137GB limit, but instead is that the low-level format has done something to them. However, I will try them again. -- Ian |
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