Scandisk & 137 GB limit

[azagahl]

Scandisk, even ME windows version, causes corruption when used on partitions located above 137 GB.

Is it safe to use scandisk on a partition at byte x < 137 GB when there is a partition with data located at x + n * (137 GB)?

Is there any way to disable scandisk from running automatically on drive X?

Should / will Unofficial SP do something to disable scandisk on such partitions?

It wouldn't be too hard to rename scandisk.exe to trashdsk.exe and then have an app named scandisk.exe that checks for partitions above 137 GB and calls trashdsk.exe only if it's safe. It sounds hacky but it's better than destroying your hard disk...

[eidenk]

Scandisk, even ME windows version, causes corruption when used on partitions located above 137 GB.

What do you exactly mean here ?

In my experience, you can define a 200 GB HDD in one single partition with Windows Me fdisk and then format and run setup and successfully install Windows and run its tools without problems including scandisk, but Windows will not write a single bit of data above the 137xxxxxxxxx bits limit (128 GB). Instead it will write the data that you want to write above the limit at the beginning of the disk and will destroy your system by overwriting files located there maybe even the FAT but I can't exactly say. It does not however overwrite the MBR, unlike what Petr said in another thread. And unlike I have said myself when relating the results of my test. I copied data on my 200/183 GB HDD formated in one partition with Windows Me running. I did use Total Copy for doing so. When I reached the 137/128 GB limit, I received errors messages saying it wasn't possible to copy anything anymore. I tried to unsuccesfully to resume copy several times. I tried then to launch some apps but all crashed by throwing a black error message on a white box (you know which ones I mean). Then explorer similarly crashed and the system was unusable. I successfully managed to reboot the disk but it didn't go past the logo screen. After that it was a full screen of random ASCII characters. I'll try to do some forensics on the drive tommorow or so to see what has been damaged.

Is it safe to use scandisk on a partition at byte x < 137 GB when there is a partition with data located at x + n * (137 GB)?

I assume that this should be safe as scandisk is not aware of partition 2 when it works on partition 1 and works within and not beyond the 137/128 GB limit.

Is there any way to disable scandisk from running automatically on drive X?

I suppose you don't ignore scandisk can be disabled from automatically running in msconfig.

One think I wonder about scandisk is what file it does use to access the file system when it is not run from within windows ? Does it still use ESDI_506.PDR ? If yes it is possible that scandisk works perfectly well for any partition size up to the 2 TB limit of the FAT32 filesystem once ESDI_506.PDR is fixed.

[eidenk]

Scandisk, even ME windows version, causes corruption when used on partitions located above 137 GB.

What do you exactly mean here ?

In my experience, you can define a 200 GB HDD in one single partition with Windows Me fdisk and then format and run setup and successfully install Windows and run its tools without problems including scandisk, but Windows will not write a single bit of data above the 137xxxxxxxxx bits limit (128 GB). Instead it will write the data that you want to write above the limit at the beginning of the disk and will destroy your system by overwriting files located there maybe even the FAT but I can't exactly say. It does not however overwrite the MBR, unlike what Petr said in another thread. And unlike I have said myself when relating the results of my test. I copied data on my 200/183 GB HDD formated in one partition with Windows Me running. I did use Total Copy for doing so. When I reached the 137/128 GB limit, I received errors messages saying it wasn't possible to copy anything anymore. I tried to unsuccesfully to resume copy several times. I tried then to launch some apps but all crashed by throwing a black error message on a white box (you know which ones I mean). Then explorer similarly crashed and the system was unusable. I successfully managed to reboot the disk but it didn't go past the logo screen. After that it was a full screen of random ASCII characters. I'll try to do some forensics on the drive tommorow or so to see what has been damaged.

Is it safe to use scandisk on a partition at byte x < 137 GB when there is a partition with data located at x + n * (137 GB)?

I assume that this should be safe as scandisk is not aware of partition 2 when it works on partition 1 and works within and not beyond the 137/128 GB limit.

Is there any way to disable scandisk from running automatically on drive X?

I suppose you don't ignore scandisk can be disabled from automatically running in msconfig.

One think I wonder about scandisk is what file it does use to access the file system when it is not run from within windows ? Does it still use ESDI_506.PDR ? If yes it is possible that scandisk works perfectly well for any partition size up to the 2 TB limit of the FAT32 filesystem once ESDI_506.PDR is fixed.

[azagahl]

Scandisk, even ME windows version, causes corruption when used on partitions located above 137 GB.

What do you exactly mean here ?

I am able to run DOS or windows ME scandisk on my partition above 137 GB. However, if it detects an error, I think it writes it in a way that corrupts the lower 137 GB. I might be wrong as I haven't exhaustively tested these scenarios, but I think that explains how my disk got corrupted. I did have trouble booting and I saw the random ascii characters on the drive (when I booted from a different drive).

Is it safe to use scandisk on a partition at byte x < 137 GB when there is a partition with data located at x + n * (137 GB)?

I assume that this should be safe

I hope you are right.

Is there any way to disable scandisk from running automatically on drive X?

I suppose you don't ignore scandisk can be disabled from automatically running in msconfig.

Yes, you can disable Scandisk starting on a bad shutdown under MSCONFIG, General, Advanced. I was wondering if anyone knew a way to restrict it to a particular disk though?

BTW, when you boot into Safe mode does Windows switch to using ESDI_506.PDR? If so, people like me that use a seperate PDR will need to be careful when operating in "safe" mode . I will test this out later...

[Tihiy]

According to Patch137 manuals, Windows scandisk and Defrag unable to work with big disks. However, DOS scandisk able. In Safe Mode, Windows uses only DOS to access HDD, so no pdr or other drivers loaded.

[eidenk]

azagahl

I am able to run DOS or windows ME scandisk on my partition above 137 GB.

How do you manage to assess that scandisk worked above the 137 GB ?

I assume you are speaking about scandisk.exe run from Dos and not scandskw.exe run from Windows.

At some point, when I was filling the 200/183 GB partition to test the 137/128 GB limit, the C Drive property sheet did grossly misreport the values of used and empty space after some crash due to my stupidity. The property sheet indicated 8Gb of used space when in fact there were around 90. However selecting all files and folders in the drive gave the right byte count. I rebooted with the floppy and run scandisk who fixed several errors. I then rebooted without problems into windows and checked that the C property sheet was indicating the right values. It was. I then resumed filling space with data until I reached the 137/128 which quickly terminated my windows session as well as my windows installation as I state above.

I cannot understand how you manage to assess that scandisk worked above the 137/128 GB limit as in my experience it is impossible to attempt to write data above this limit without corrupting files on the partition.

Please could you be more precise as to what you exactly did and what happened ?

I did have trouble booting and I saw the random ascii characters on the drive (when I booted from a different drive).

Do you mean you saw random ascii character when you used a disk editor to look at the data on some particular sectors of your trashed partition ?

If so, people like me that use a seperate PDR will need to be careful when operating in "safe" mode

I am curious. You say you are using a special PDR file. Which one and for which reason ?

Tihiy

According to Patch137 manuals, Windows scandisk and Defrag unable to work with big disks. However, DOS scandisk able. In Safe Mode, Windows uses only DOS to access HDD, so no pdr or other drivers loaded.

He claims Microsoft claims 512 GB limit for those tools. Does all this mean that there is no problem for working with DOS beyond the 137/128 GB limit ? Could I theorically fill the disk with data beyond the limit witout corrupting anything with DOS only ?

Something that may be of interest to you : the GPL fix for LBA48 adressing for the Xbox. Xbox FAT32 drives are properly handled beyond the limit with it. Xbox Tool, Breaking The 137 Gb Limit, Can we update the IDE driver ?, Largest Hard Drive Still 137gb ?

[azagahl]

Sorry eidenk, I think I have more questions than answers. Basically my hard disk got trashed a few days ago and I am sure it has something to do with the 137 GB limit.

How do you manage to assess that scandisk worked above the 137 GB ?

Scandisk seems to process the partiton above 137 GB normally. However, in my case, I think the FAT is located just below 137 GB (the partition starts before there) and the majority of the partition lies above 137 GB. So maybe scandisk is grabbing the FAT correctly but if it sees an error (cross-linked files or something?) and tries to make a correction it might mess up?

I am not aware of any situation where my PC should be using ESDI_506.PDR. So I don't fully understand why my disk got corrupted a few days ago. I did run scandisk on the high partition shortly before the corruption appeared, so I am afraid of runnig scandisk/defrag on that partition now.

I assume you are speaking about scandisk.exe run from Dos and not scandskw.exe run from Windows.

I think it was scandisk in Windows caused my problem. I've run Windows defrag on that partition without noticing any problems, so I am not sure what happened exactly.

Do you mean you saw random ascii character when you used a disk editor

No, I just did "dir X:/" (where X represents my normal boot drive) and it showed piles of garbage characters. Good thing I had images saved with savepart.

I am curious. You say you are using a special PDR file. Which one and for which reason ?

Actually I seem to be using an MPD file and not a PDR file, whatever those extensions mean. In my Hard disk controller driver file details, it lists "viadsk.mpd" and "ios.vxd". This is from installing the latest Via Hyperion drivers for my VIA motherboard (K8T Neo Fis2R). This is the only way I know to get my hard drives running at full speed (Ultra ATA 100) in Windows.

[RJARRRPCGP]

I did have trouble booting and I saw the random ascii characters on the drive (when I booted from a different drive).

Do you mean you saw random ascii character when you used a disk editor to look at the data on some particular sectors of your trashed partition ?

That person saw random characters for the directory listing when using the dir

command in DOS.

I saw that symptom before on a PC, but that was because of the HDD jumper setting. Using the wrong HDD jumper settings can cause that symptom to occur.

[HyperHacker]

Basically the problem here is a lack of LBA support. Before LBA all drives used 28-bit addressing. The problem is you can't address anything higher than 137GB with only 28 bits. When Windows tries to, it chops off the number and sends only the first 28 bits to the drive, so when you try to access the 138th GB, you really end up accessing the 0th. LBA mode expands the address to 48 bits so the drive gets the proper number.

[Petr]

Basically the problem here is a lack of LBA support. Before LBA all drives used 28-bit addressing.

<{POST_SNAPBACK}>

This is wrong. There are two different LBA modes - classic 28-bit and newer 48-bit., but both of them are LBA.

Both old CHS addressing and newer LBA (28-bit) addressing use the same 28 bits, but in different manner.

The rest what you wrote is correct, I just want to emphasize that 48-bit LBA is not the same as LBA.

Petr