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This is one of those things that start gnawing at you once you know too much. In my case, I've been building up x86 assembly, PC hardware, and compression algorithm knowledge for the last two decades, and today, when copying some files onto a floppy, all of that converged and assaulted me with a single question:
Which DOS-era diskette-based backup program was the best?
I've always admired a certain class of backup programs: Programs that directly manipulated the floppy controller at an extremely low level to format and write data in one pass, and doing so while the computer was performing other work like reading from the hard disk, or compressing the data -- or both. Getting all of that working simultaneously, faster than the native operating system, was truly a site to behold. It was during this admiration that a couple of things hit me: There is a tiny resurgence of classic PC computing going on; people such as myself, Mike Chambers, Mike Brutman, Dave Dunfield, and many many others are actively programming for older x86 computers, on older x86 computers. I also realized that sometimes your development computer of choice can't (easily) connect up a ZIP drive or network card for backups -- but that's no excuse to not back up your work in progress. So, we use a backup program. And we come back to the question: Which one was king?
The only DOS-era programs I could remember that achieved all of the above were Norton Backup, Fifth Generation Systems' Fastback, and Central Point Backup (also formerly known as PC Backup). Thanks to a friend, I was also reminded of (and given the opportunity to test) the original Fastback from 1984. I tested all of them, and just for comparison I tested a "home-grown" solution of pkzip, xcopy, and batch files.
The test backup set was representative of a hobbyist programmer's project tree: 1410KB in 192 files spread across 5 directories, consisting of mostly source code and a few binary files. Without compression or error-correction, it fills 4 disks completely, and overflows onto a 5th disk by about 4K. This tiny overflow was intentional, so that "light" compression settings would have a chance to always work and reduce the target disk set by at least one disk.
The philosophy behind the test was the daily work of a hobbyist programmer: You back up every night. You want it go fast so that it doesn't become a burden. You always want a form of error correction so that you can tolerate a few fliipped bits. You employ grandfather-father-son backups, so you're always reusing disks. These are short-term backups only, to prevent loss of your recent work. These concerns translated into the following settings:
Test setup:
Best sizes and best times are green, worst times are red
| Program | Proprietary Disk Format | Compression: None |
Compression: "Save Time" |
Compression: "Save Disks (low)" |
Compression: "Save Disks (high)" |
|---|---|---|---|---|---|
| Fastback v5.13 Fifth Generation Systems, 1984,1985 |
yes | 4 disks 1m18s (1084KB/m) |
(not offered) | (not offered) | (not offered) |
| Fastback Plus v2.01 Fifth Generation Systems, 1988 |
no | 5 disks 1m59s (711KB/m) |
5 disks 1m51s (762KB/m) |
(not offered) | 3 disks 4m33s (309KB/m) |
| Norton Backup v1.2 Norton Computing, 1990 |
no | 5 disks 1m44s (819KB/m) |
5 disks 1m35s (897KB/m) |
3 disks 3m07s (455KB/m) |
3 disks 7m09s (198KB/m) |
| Norton Backup v1.2 Norton Computing, 1990 |
yes | 5 disks 1m33s (916KB/m) |
5 disks 1m30s (946KB/m) |
3 disks 3m04s (463KB/m) |
3 disks 7m07s (199KB/m) |
| Microsoft Backup 6.0 Bundled with MS-DOS 6.22 (C) 1991-1993 Symantec and Quest Development Technology from Norton Backup |
no | 5 disks 2m40s (578KB/m) |
3 disks 4m17s (403KB/m) |
(not offered) | (not offered) |
| MyBackup 1.0.0 MySoftware Co. |
no | 5 disks 3m19s (425KB/s) |
(not offered) | (not offered) | (not offered) |
| PC Backup (PC Tools 6) Central Point Computing, 1990 |
no | 5 disks 1m39s (851KB/m) |
5 disks 1m32s (907KB/m) |
(not offered) | 3 disks 3m00s (467KB/m) |
| PC Backup (PC Tools 6) Central Point Computing, 1990 |
yes | 5 disks 1m32s (908KB/m) |
4 disks 1m28s (928KB/m) |
(not offered) | 2 disks 3m00s (466KB/m) |
| Central Point Backup (PC-DOS 2000 version) Central Point Computing, 199? |
no | 5 disks 2m13s (630KB/m) |
3 disks 5m15s (266KB/m) |
3 disks 4m59s (280KB/m) |
3 disks 6m05s (230KB/m) |
| Central Point Backup (PC-DOS 2000 version) Central Point Computing, 199? |
yes | 5 disks 4m05s (343KB/m) |
2 disks 5m14s (267KB/m) |
2 disks 5m02s (278KB/m) |
2 disks 6m05s (230KB/m) |
| For comparison only | |||||
| "Roll your own" backup PKZip + CHUNK + XCOPY |
no | 4 disks 4m16s (332KB/m) |
2 disks 6m0s (236KB/m) |
(not offered) | 2 disks 10m4s (141KB/m) |
Final Opinion: For a programmer making daily backups of a project, either Fastback Plus or Norton Backup with compression set to "save time" is best.
As to whether or not you should use a proprietary disk format, I think I personally would. The savings are noticeable to the naked eye, and since the backup data is in a proprietary format anyway, you'll need the original program to extract the data -- and the original program understands the proprietary format. If you're concerned with portability, then you shouldn't be using these programs and should instead be "rolling your own" with RAR, ARJ, ZIP, etc. in disk-spanning mode. Portability wasn't the point of this test; this test was focused toward short-term backups only.
Fastback's proprietary format is similar to Central Point Backup's format, except all 40 tracks are 10 512-byte sectors. This results in a non-readable diskette to DOS (attempting a DIR results in Sector Not Found) but also results in the most usable space (400KB) and is the reason it was able to fit the uncompressed test suite onto four disks instead of five.
Examining a Fastback proprietary format disk shows that the program does not perform any compression (9 of the 10 sectors contained uncompressed data, and the 10th sector contained data plus ECC data).
Fastback was the fastest program of all tested, but it suffers a bit more from age than the others. It only supports 5.25" disks (both DD and HD) and only one backup catalog (I guess in 1984 they didn't assume people would eventually have more than one hard disk in a system). Fastback Plus was much more flexible and, although not the speed king, is recommended over the original Fastback for practical modern usage.
Fastback and Fastback Plus had better user change-disk prompts, displaying a flashing "Insert volume X" while the prior volume was being written to. Norton Backup and Central Point Backup only remind the user to switch disks right at the very second they need the new disk, which isn't very friendly.
Norton Backup's "proprietary" format differs from a regular DOS format in that it can squeeze a tiny bit more information onto the disk at the expense of not being as tolerant of flaky disks and/or timing. Regular DOS format is 9 512-byte sectors, which is 354KB usable space (6K is used for FAT housekeeping); Norton Backup uses 5 1024-byte sectors for 39 of the 40 tracks, which results in 390KB usable space. The directory of the disk contains entries that spell out "This is not a DOS disk. This is a Norton Backup disk. Do not use."
One of my testing diskettes went bad in the middle of testing Norton Backup. Even with verification turned off, Norton Backup detected this and very gracefully handled reworking the backup for a new disk, even going as far as to tell me I had inserted a disk already part of the backup set currently in progress, even though I had erase-without-prompting turned on. Impressive handling!
Microsoft Backup should produce equal results to Norton Backup using Save Time compression, since the technology is identical. However, MSBACKUP took at least 20 times longer to read information from the hard disk thanks to a very long startup time and also seemingly lacking the ability to read from the hard disk while simultaneously writing to floppies (a feature shared by all other programs in the test suite). On the test platform (a true blue IBM XT), it paused for over a minute to fill internal buffers, wrote to diskettes at normal speed, then paused again for well over a minute. With such inexplicable long pauses, and the lack of multitasking, it turned in some of the worse performance in the suite.
MSBACKUP removes two of the backup options (it only supports Full, Incremental, and Differential) and also does not support any proprietary disk format.
MyBackup is one of those $10 programs you used to be elated to find in the cheap section at Babbage's when it was still around. One of the many pieces of software from MySoftware Co., it (like the others) is a simple program with simple controls used to perform simple tasks, directly and without confusing users. The interface is a bit clunky, but it works better than rolling your own backup solution.
There is no way to turn off verification of data, which is why it is not the speediest of the bunch. It also requires "formatting" diskettes if you haven't run them through the program already (it doesn't matter if they're formatted or not; MyBackup wants to write some signature to the disk somewhere).
MyBackup holds the very interesting and unique distinction of being the only backup software in the test to store the backup files in an accessible state. Backed-up files show up on each diskette's directory, and there is a helpful text file on each diskette that shows you what disks your files are on. I assume that files that are bigger than a diskette are split across diskettes, but I neglected to put such a file in the test suite so you'll have to test for yourself.
Central Point's PC Tools 6 includes PC Backup, which is notable for 1. Taking a very long time (over 90 seconds) to scan the hard disk for directories when it starts up on an 8088, and 2. totally making up for that by supporting the Central Point Option Board to speed up diskette format operations by nearly 50%. The interface was quite adequate, being easy to understand for most user levels.
PC Backup's "proprietary" format is similar to Norton Backup's format, except that instead of using 5 1024-byte sectors on 39 out of 40 tracks, it uses 10 512-byte sectors on every track of the disk. The amount of usable space is the same. Interestingly, it does not pretend to be a DOS disk at all and doesn't contain a "fake" directory with a message to the user (trying to read it returns "NON-DOS diskette"), but it does contain a boot block that prints out "This disk can't boot: it was formatted by PCBACKUP. Change Disks and Press a Key." if booted.
A pack-in with IBM PC DOS 2000, Central Point Backup's interface was the most functional and pretty. It was also slower than the others, which, combined with the generally lackluster file reading speed, made Central Point Backup the slowest program in the test. It is possible that this uneven speed contributed to the program taking longer with "save time" compression than "save disks (low)" compression (!).
Central Point Backup's "proprietary" format is similar to Norton Backup's format, except that instead of using 5 1024-byte sectors on 39 out of 40 tracks, it uses 10 512-byte sectors on every track of the disk. The amount of usable space is the same, as is the "Do not use this diskette" directory message.
While I had an Option Board in the test computer (see "PC Backup" above for why this is significant), support for it seems to have been removed in this PC DOS 2000 pack-in version.
Fastback Plus's and Norton Backup's "save time" compression is fascinating in that it compressess better the more time it has. For example, when testing Norton Backup set to "always format and verify", the format process took longer and "save time" took advantage of this extra time to fit the data onto three disks. When set to "only format if necessary" (much faster), it didn't have enough time to perform much compresson and the backup fit onto five disks. But, as the times reflect above, "save time" in both cases really did save some time. It is assumed that "save time" would be more effective on faster computers, or if formatting is a necessary requirement.
Always operate both programs in "advanced" mode; otherwise, many vital options (such as compression) are hidden and unchangable.
If you want to "roll your own" backup and force formatting on, you too can use a "proprietary" format if you use FDFORMAT to format each disk with only 16 root directory entries instead of the usual 112. This gives each diskette 5K more in usuable space (ie instead of the normal 362492 bytes (354KB) after a DOS format, 367616 bytes (359KB) are available).
Norton Backup and Fastback did not display years over 1999 properly when backing up, but restored them correctly.
Both Norton Backup and Central Point Backup/PC Backup utilize Stac compression libraries for their compression routines.