Users of hard disks and removable cartridge drives with FWB's Hard Disk ToolKit (HDT) driver software version 1.3.1 or earlier should be aware of a potential data loss problem while using disk optimization software or other programs that move or access data in chunks larger than 32 MB. This specific problem does not occur with HDT 1.5.0, 1.5.1, and the current version, 1.6.0; FWB fixed the problem in 1.5.0 without any reports of data loss up to that point.
Data loss only occurs in a limited set of circumstances, in which very large amounts of RAM are available to the software moving data. The problem cannot occur on a Mac with less than 32 MB of RAM, and is unlikely even on systems with considerably more than 32 MB of RAM.
Most programs, even when using large files, read and write them in small pieces. (For example, Photoshop moves data in pieces no bigger than 32 kilobytes, not megabytes.) It's not a good idea for developers to attempt to transfer 32 MB in a single pass, anyway. Assuming a SCSI bus could transfer data at 3 MB per second, a 32 MB read would freeze the Mac for over ten seconds, which would confuse or concern most users. In addition, such freezes could cause network time-outs, especially if virtual memory was involved.
Instances of data loss that may be attributable to this problem have reportedly occurred while using Symantec's Norton Speed Disk 3.0 or 3.1, part of the Norton Utilities for Macintosh package. (This is NOT related to an earlier problem reported with Norton Speed Disk 3.0 in TidBITS-243. The earlier problem is fixed in 3.1.) Two other programs have been identified that might run into this problem - SpeedyFinder 7 users should turn off the option that allows the program to use all available RAM and Maxima users with large RAM disks should turn off the option to use the image transfer method and should use file-by-file instead.
If you have a hard disk or removable cartridge drive and are running a version of HDT earlier than 1.5.0, I strongly recommend upgrading to a later version (such as 1.6.0) to avoid potential problems. If you have a version of Hard Disk ToolKit earlier than 1.5.0, you must order the update directly from FWB. The price for the full version upgrade is $39 plus shipping and handling (and sales tax if in California). Shipping and handling is $4 in the U.S.; $10 outside. You may order by phone, fax, or email with a Visa, MasterCard, or American Express or by mail with a check or money order. Please be sure to include your serial number when ordering. Hard Disk ToolKit Personal Edition customers can upgrade for $29 plus shipping and handling, etc. If you have version 1.5.0 or later, you can upgrade free of charge if you fax FWB a copy of your original invoice, with your serial number written on it. Finally, upgrades are free for those who purchased Hard Disk ToolKit or Hard Disk ToolKit Personal Edition after 01-May-94.
If you use a hard disk or removable cartridge drive with formatting or driver software older than a few months, check with the software's developer to verify that the driver is up to date. According to Casa Blanca Works, their Drive7 software (and versions 3.0 and later of APS Power Tools, which uses the same code) does not suffer from this problem. Although we don't have specifics, other drivers may suffer from similar bugs, so to be safe, make sure you have the latest version of your driver software and avoid the operations mentioned above which may attempt greater-than-32 MB transfers, if you have more than 32 MB of RAM installed in your Mac.
HDT comes with hard disks and removable cartridge drives manufactured by FWB. It is also sold as a retail software package and used to format third-party hard disks. If you are not sure whether HDT has been installed on your hard disk, select the icon for the disk and choose Get Info from the File menu in the System 7 Finder. If HDT formatted the disk, the Where line will include "FWB" and the drive's SCSI ID (which is not relevant). The Where line will end with HDT's version number.
Given the recent problems Symantec has had with Speed Disk 3.0, I would like to stress that this is not inherently a problem with Speed Disk, but with an older version of FWB's driver software. Speed Disk 3.1 is safe to use (with proper backups) in the vast majority of user configurations. I commend Symantec for their quick analysis and response to the situation.
FWB -- 415/474-8055 x656 -- 415/775-2125 (fax)