PROBLEM ALERT:  MS-DOS HARD DISK HANDLING FLAW FOUND
 
	There is a problem in the way that MS-DOS versions 2.05, 2.11, and 3.1 handle hard disk errors on the Rainbow.  Fortunately, there is also a solution.
 
Background
 
	Hard disks go through very stringent testing by their manufacturers.  Actual or potential problem areas (for example, a tiny flaw in the oxide) are identified on special tracks on the disk, and on its label.  It is then up to the user of the hard disk to run software that will check out the disk before putting data on it, to see which of the "manufacturer's suggested bad spots" are actually bad enough to cause operating problems, and to mark them so they won't be used by the operating system.
	The software to handle all of this is normally part of the operating system, built into the initializing and formatting routines for the hard disk.  Basically, the steps involved for setting up a new hard disk are:
 
1.  Initialize the hard disk.  The software will check out the physical surface of the disk and, if it finds a sector that it cannot read, will note that track and sector number in the Bad Address Table (BAT).
2.  Partition the hard disk.  The software divides the hard disk into logical drives which can be used for different operating systems.
3.  Format each partition.  This involves writing the chosen operating system information into each partition and preparing the partition to receive data under that operating system.  During this process, the format utility will also check the Bad Address Table.  If a track and sector in the BAT corresponds to a location within that partition, the format utility will mark the entire cluster as bad, and will identify the bad cluster address in the File Allocation Table (FAT).
4.  Once the partition is formatted, MS-DOS then uses the File Allocation Table to determine where to write new data.  It will not use any clusters identified as bad, so the user will not risk putting data on a bad sector.
 
	These steps are normal parts of every computer's hard disk setup and maintenance process.  The fact that your disk contains bad sectors should be of NO CONCERN so long as these bad sectors are correctly identified and mapped in the File Allocation Table, to prevent their usage.
 
	Suitable Solutions has discovered that Rainbow MS-DOS does not function correctly when handling hard disks.
 
Error Mapping with FORMAT
 
	The first part of the problem lies in the FORMAT utility.  After long hours of researching some elusive problems with a 40 megabyte hard disk, Suitable Solutions discovered that the MS-DOS FORMAT utility provided by DEC marks the bad cluster information into the FAT "one off."  The cluster that MS-DOS marks as bad is actually the one FOLLOWING the bad cluster.  Thus, if you have a bad sector identified in the BAT as cluster 2000, FORMAT will read is as 2000 but write it to the FAT as cluster 2001.
 
Error Reporting with MS-DOS
 
	The second part of the problem lies in the reporting of hard disk errors under MS-DOS.  Normally, if a sector on a disk goes bad, MS-DOS should detect the problem when trying to read or write data on that sector, and issue a warning message with the standard "Abort, Retry, Ignore" options.  The user can then use the RECOVER command to save as much of the affected file as possible and mark the sector so it won't be used again.
 
	Suitable Solutions has also discovered that MS-DOS does not report hard disk errors correctly.  Thus, when you run across a bad sector (that FORMAT incorrectly identified as good), DOS will not let you know it.
 
Don't Panic
 
	Yes, this is a serious problem.  If you have been mysteriously losing data on your hard disk for no apparent reason, there's a chance that you have a bad sector on your disk.  THERE ARE SOLUTIONS TO THIS PROBLEM.
	First of all, you need to know WHETHER you have any current problems with your hard disk.  Second, you need to RECOVER any files that may be damaged.  Third, you need a way to PREVENT any future problems from developing.  And last but not least, you should have a way to MAINTAIN the health of you current (or future) hard disk.
	Suitable Solutions is working to solve these problems.  Included with this issue of RAINBOW NEWS is a diskette (Note:  the diskette, generously provided by Suitable Solutions, has been included with issues mailed to paid up IRUG members during the journal's initial mailing only) containing the following:
 
Patch program HDRPT to enable MS-DOS 2.11 or later to report hard disk errors.
 
Patch program HDSCAN to allow you to scan your hard disk to see if you have any bad sectors on it.
 
READ.ME file with information for using these programs.
 
	These programs will also be available on the IRUG bulletin board and in the WARUG software library.  (If you know of other Rainbow owners with hard disks, please let them know that these programs are available.)
	Program HDRPT solves the problem of MS-DOS error reporting.  Program HDSCAN allows you to determine whether or not you have one of more bad sectors on your disk currently.  The MS-DOS RECOVER command (DOS version 2.11) can prevent an identified bad sector from being used again.
 
WARNING:  Don't use the RECOVER command unless you are absolutely certain you know what you are doing.  Used correctly, RECOVER will mark the bad sector in a file and rebuild the rest of the file (minus the part of the file that was in the bad cluster).  USED INCORRECTLY, RECOVER WILL WIPE OUT EVERY SUBDIRECTORY AND FILE NAME ON YOU HARD DISK.  RECOVER must be used with a filename.  Otherwise the contents of you hard disk will be essentially destroyed.  Do not use RECOVER under any circumstances without backing up your entire hard disk first.  See the MS-DOS 2.11 Advanced User's Guide for more information.  Also read the READ.ME file on the enclosed diskette.)
 
	For ongoing hard disk maintenance, Suitable Solutions recommends the use of the DISKTEST program of the Norton Utilities, which runs on the Rainbow with the /D2 option.  [The /D2 option is not necessary to run DISKTEST - ed.]
	This is the information that is available as Rainbow News goes to press.  By the time this issue is ready to mail out, however, there will very likely be additional information on both the problems and solutions.  The READ.ME file on the diskette will contain the latest information.
 
IMPORTANT:  Read the READ.ME file on the diskette before attempting to use any of the software.  This file will contain detailed, step-by-step instructions as well as any further information available on the problems themselves.
 
Looking Ahead
 
	Suitable Solutions has reported this problem to Digital, and their software engineers are researching it.  In the meantime, there is no need to panic.  There's a good chance that you have NOTHING TO WORRY ABOUT, and HDSCAN will let you know if you do.  If it turns out that you DO have a problem, you should be able to resolve it with the information provided on the enclosed diskette.  Additionally, if you are a DEC maintenance customer, you may want to inform Atlanta and.or your local Field Service office of any problems you run across so they will be able to gauge the severity of the situation.  And, of course, if you have not already developed a regular backup procedure for your most important files, now is a good time to do so.
 
