DISCTEC

REMOVABLE HARD DRIVE OBSERVATIONS

Over the years, DISCTEC has received many removable hard drives as RMA material.  We have found that some of these drives were not really "bad".   The drive was physically alright, but the partitioning and format of the drive were corrupted.

We also understand that internal and removable drives should and must be handled/treated differently.  Any shock which the RHD receives is the most frequent cause of failure.

Here then are some suggestions and techniques that DISCTEC uses to either recover or declare the hard drive in question as "recoverable" or "bad".

Some of these suggestions will be in the form of questions. This will aid in the steps to recovery or declaration.

1.  When inserted in the docking bracket, does the LED light on the removable cartridge light up and then go out?

A. If YES, this may be good.

(1.) At the same time the light is on, is the drive noisy? Scraping or grinding noise while the platters attempt to spin up. (This is usually a bad sign.)

B. If NO, this may be a drive that does not  spin up upon insertion into the docking bracket.

Note: Some manufactures treat power application differently.   (Not good/Not bad/Just different.)

2. Does the light come on and never go out?

A. If YES, the drive may not be reaching operating speed, and therefore not reporting a READY condition to the host machine. This may not be a good sign. Most of the time, this is a result of physical damage.  Very few people drop their computers; many people drop their removable hard drives. (Not a fault - Just a fact.)

3. If a drive letter has been assigned, can you read or query the drive? If YES, run the CHKDSK or SCANDISK command to see if there are any file system problems or bad sectors  reported.

A. If YES, file system problems or bad sectors are reported, then there are usually a couple of causes for this to happen.

(1.)  The drive has been dropped, and physically damaged.

(2.)  The drive has been removed from the docking bracket with files left open - data not written back to the RHD from the file system's memory cache.  SCANDISK will report file system problems, which should be repairable.  Information in the affected files may be lost.  SCANDISK should not report bad sectors during the surface test.

(3.)  The drive is physically beginning to fail, either electrically or mechanically.  The firmware in some drives has the ability to reassign bad sectors to an unused area at the end of the disk.  All extra sectors have already been allocated to replace previous bad sectors.

4. Is the drive used in more than one host machine?

A.  If YES, is the drive being used under more than one operating system (OS)?  Always use the FAT16 file system originally introduced with DOS if you need to use an RHD drive under more than one operating system.    All versions of Windows can read and write a FAT16 prepared RHD drive.

B.  Do any of the machines auto-detect devices when booted?  Auto-detection now has a double meaning.  Besides detecting the head/cylinder/sector values of the drive, the ROM BIOS must also negotiate what protocol to use when transferring data between the drive and the host.  Negotiation will determine whether the drive will use PIO mode 1-4 or a form of UDMA.  It is interesting to note that a ROM BIOS will negotiate a transfer protocol with a device, but does not verify the mode with a transfer test.   Occassionally, it may be necessary to slow down the transfer mode.   It is also important to note that swapping to a different RHD without rebooting can cause problems if the new RHD is not capable of the mode originally negotiated by the ROM BIOS at boot time.  Alway boot with the oldest, slowest RHD to allow negotiation of the safest transfer mode.

C. Are there parameterization setup differences? The ROM BIOS has the responsibility of presenting acceptable logical values for the number of heads, cylinders, & sectors to the operating system.  These logical numbers must be translated from the physical numbers presented by the firmware of the RHD.   This translation can be accomplished using LBA, ECHS, or CHS on older machines. (LBA being Logical Block Address, ECHS being Extended Cylinder Head Sector, CHS simply cylinders heads and sectors)  Some ROM BIOS's allow the user to specify the translation method.  Newer ROM BIOS's will auto-detect the parameterization of the RHD.  Once again, all  ROM BIOS manufacturers may not parameterize a particular   RHD in the same way.  Writing on an RHD which has not been detected correctly will usually cause corruption in the file system and loss of data in any files affected.

D.  Are the ROM BIOS's of the hosts different or do they have different version/release dates?   Different ROM BIOS's may treat the same RHD differently.  One machine may not yeild the same parameterization or may not negotiate the same transfer mode as described above.

E. Is the DISCTEC device driver, DISCTEC.SYS, used on any of the machines?  The latest version of the DISCTEC.SYS device driver will try to react to what the boot sector on the RHD indicates is the parameterization.    The DISCTEC

Note: Older drives of the 520 MB capacity (on the front label) may actually be a larger capacity than the RHD has been partitioned. The DISCTEC partitioning of 504 MB and a signature were installed on all RHD drives up to 520 MB at the manufacturing facility. Older systems which lacked auto-detection capabilities used the DISCTEC partition to allow RHD drives of various capacities to be booted without altering the ROM BIOS setup parameters. This was accomplished by setting the ROM BIOS to a "Type 2".  Newer ROM BIOS's which auto-detect this 520 MB drive may have a problem accepting this DISCTEC partition.  If the 520 MB drive will be used exclusively on machines with auto-detecting ROM BIOS,  use fdisk to remove and recreate a new partition allowing the ROM BIOS to determine the RHD's characteristics.

HOT Swapping RHD drives

DISCTEC's RHD drives are designed to allow the interchange of various capacity RHD drives without rebooting the machine.  DISCTEC refers to this as "HOT" swapping RHD drives.  DISCTEC requires the use of the device driver, DISCTEC.SYS, to allow "HOT" swapping under DOS.   "HOT" swapping of the boot drive "C:" is no longer a practical solution under the Windows 9x or Windows NT operating systems.  The newer OS will have too many sytem files open on C: to allow the RHD to be removed without shutting down the OS to close these files.  Even with Windows 3.1 and its swap file, great care must be exercised in removing an RHD which is the boot device C:.  "HOT" swapping of RHD drives is only recommended under Windows 9x when the RHD is not the drive letter that Windows 9x is installed on.  Configuring the RHD bracket as the Master of the Secondary IDE bus is usually the best solution to allow "HOT" swapping.

Steps to attempt RHD recovery if the drive spins up but no drive letter:

It may be advantageous to boot from a floppy with necessary utilities and files installed, for the first try DISCTEC prefers DOS and uses 6.22. By doing this many of the mentioned problems are taken out of the diagnostic procedure.

1. After booting from a diskette, use the FDISK command to look at the RHD's existing partitioning information, there are a couple of very important facts here. (Make sure you first choose the correct hard disk before looking at its properties.)

A. Are there multiple partitions? Primary partition and Extended partition with logical drive letter(s).

B. Is the file system of the partition set up to be FAT16 (file allocation table) or FAT32?  Only Windows 9x and Windows 2000 can read FAT32.

C. Is the file system DOS or something other HPFS, NTFS, ETC., ETC.?

D. Is the partition ACTIVE? This flag must be set in the partition table entry for the primary partition if the RHD drive is to be bootable.   (The RHD must also be formatted with the system option specified to boot.)

Note: Only one primary partition may be active on a drive, under normal conditions only the drive "C" (hard disk 1) will be marked with the active status when using the FDISK utility.   DISCTEC has a utility to make any primary partition active, regardless of being drive "C" (hard disk 1) or not.   Setting the ACTIVE flag will only determine whether the partition is bootable.   This does not alter the file system or the contents of any files on the RHD drive.

2. If you have multiple partitions or non-DOS partitions/fi4le systems,  delete all partitions and drive letters.  (This assumes that the data files on the RHD have been backed up prior to removing any partitions, otherwise they will be lost.)   It is much easier to test the drive if all we concern ourselves with is a single primary partition.  After deleting current partitioning,  reboot the computer from floppy again.

3. Use FDISK again to make one primary partition on the RHD. Answer Yes to make the partition as large as possible, 2047 MB will be as large as DOS FAT16 will allow. Reboot the system from diskette, then FORMAT the newly created partition.

4. Use the the following syntax for the to invoke the format command:

FORMAT x:/u/s

where "x" is the drive letter of the RHD under test, "u" tells the utility to do an  unconditional format, and "s" speifies to install the system files( Required to make the RHD Bootable).

NOTE:  Be careful if your removable hard drive is NOT the ONLY disk drive in the system, as all of the commands will destroy all data on the drive upon which they are executed.  MAKE SURE THAT IF FDISK HAS A MENU SELECTON #5, SELECT THIS FIRST TO CHOOSE WHICH HARD DISK WILL BE AFFECTED.

The procedures described above are for RHD drives that do not require the special DISCTEC partition sector. These RHD drives will be used on machines that can auto-detect the RHD or that the ROM BIOS setup has been configured specifically for the RHD drive inserted.

If your computers's ROM BIOS does not offer "auto-detection" of RHD drives, you will have to use the DiskTest (DT) Utility to write the DISCTEC signature and the special DISCTEC partition information which allows auto-detection. Next, the Machine will have to be configured for  the CMOS to contain the setting for a Type 2 hard drive, which will reflect a 20mb drive.  This is OK as the special code in the DISCTEC partition sector is looking for these parameters to be set in the ROM BIOS.

DISCTEC has been successful using the NORTON (tm) Symantics Utilities, both for viewing and repairing problems on RHD drives thought to be "bad".

To view drive using the NORTON DISK DOCTOR commands follow on screen instructions. There are other utilities that will work.  If they are available, use them.

Start the drive test on a freshly formatted drive.   You will see any possible bad areas that were marked by the FORMAT command.

DISCTEC has had success in recovering these areas with NORTON (especially if they were created by removing the drive with files open).   The syntax to use the NORTON WipeXXXX may vary depending on the version of NORTON that you have, the results are the same.

After the complete "wipe" of the RHD has been performed, you may either re-format or use the DISK DOCTOR again, the results will somewhat prove that either the drive has been recovered successfully or that there is permanent physical damage on the RHD's platters.  It will be the responsibility of the user to determine if the bad areas are too numerous for continued use of the RHD drive.  DISCTEC makes no determination as to number of errors that "are" or "are not" acceptable.  It is also helpful to attempt to determine if the cause of the errors were from a one-time shock or from continued deterioration of the drive.  To determine if the drive is beginning to fail, run the same tests later and compare results.

For those RHD drives used for the storage of "classified" data,  degaussing of the RHD may be necessary to destroy all traces of the "classified" information.  There may be other steps that DISCTEC can help with.

If you wish to attempt to remove the drive from the case, be aware that there are electronics inside for mechanical and electrical translations to make the RHD drive removable.  Opening the RHD should be done with DISCTEC personnel on the phone, to aid in the removal, the identification, and the explanation of any parts found like the Header.  Most of the time, parts will be destroyed during this process.  After identification, DISCTEC can ship the necessary replacements both for testing and final closure of the RHD.

DISCTEC understands that these procedures are tedious and time consuming (we have been doing them for 10 years), but they may give new life to a previously assumed "bad" drive.

The DISCTEC following utilities may be downloaded from this website:

1. DISCTEC Device Driver for internal installations of the RHD

2. DT (DiskTest) utility for creating the special DISCTEC auto-detection partition

3. PARTACTV (Utility to set a partition as being ACTIVE/"BOOTABLE"

Hard Drives Technical Specifications