Desktop Checker™ is provided to you by Salient, the makers of the industry-standard DiskDoubler™. DiskDoubler™ effectively doubles the space on all your disks. It's so easy to use you can "install it and forget it". The list price of DiskDoubler is $79. A best-selling product, it is available from most mail order houses and computer stores.
Desktop Checker™ may be freely distributed for non-profit use, provided it is distributed in its original self-extracting form or in DiskDoubler format. We expressly prohibit distribution in other forms, including any compression format other than DiskDoubler. For-profit use requires that you contact Salient for licensing.
Desktop Checker is a simple program that counts the number of resources in the desktop file. It is not needed for System 7.0, or if you are running Apple's Desktop Manager, since the Desktop file is not used in these cases.
Why count the resources? The Macintosh Finder cannot store more than 2727 resources in the desktop file. Exceeding this number may cause system crashes and possible file corruption. By counting the resources in the Desktop file, you can determine if you are approaching this limit. If you are approaching the limit, we recommend obtaining a copy of Apple's "Desktop Manager", an INIT that is provided with AppleShare™. Desktop Manager eliminates the 2727 resource limit. In general, unless you have a large disk (300+ MB), you probably won't exceed the resource limit.
Many details about how disks work are hidden from you because you usually don’t need to know about them. However, there are some aspects of a disk that you should know about because of shortcomings in current Apple System Software.
Disks vs Volumes
Loosely defined, a disk is a round piece of magnetic or other media which is used to store files. For example it could be a floppy disk, a hard disk, or a cartridge from a removable optical or magnetic drive (these items may have a rectangular package, but are round inside).
A disk is usually composed of a single volume, which is identified by the icon that appears on the desktop when you turn on your Macintosh. However, a disk can be divided into multiple volumes, in which case an icon for every volume appears. You can think of volumes as representing a certain portion of the space available on the disk; different volumes each use a different portion of the disk, and space may not be shared between them. As far as the Macintosh is concerned, they are just as separate as physically separate disks.
Volume Block Size
The volume block size is the minimum size chunk that must be used to allocate space on a volume. For example, with a block size of 2K, any file that is from 0 to 2K must occupy at least 2K, because space is allocated in 2K blocks. Some files have two “forks” (resource and data) and each fork is allocated separately. Thus, with 2K blocks, a tiny file might occupy as much as 4K of the volume. As a guide, here are minimum block sizes for various volume sizes; these figures may vary slightly, depending on the formatting software and the exact size of the volume:
0-60MB 1K
60-130MB 2K
130-180MB 3K
180-240MB 4K
240-320MB 5K
There is an easy way to figure out the block size of a volume:
(1) create a very small file, say 10 bytes, using any program,
(2) use the Finder’s Get Info command to see the size on disk.
Managing Disk Space and Avoiding Disk Problems
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Finder problems with too many files
The current system software that Apple provides is just not up to the task of managing more than a few thousand files before various problems start to occur. Aside from serious performance problems with large numbers of files, there is another far more serious limitation. The Finder stores information about your files in the Desktop file. This file has a limit of 2727 “resources”. When this limit is exceeded, the Finder won’t warn you—it will just start to crash frequently and may even corrupt some of your files when you perform a Copy or Duplicate operation.
Each application adds at least 3 resources to the desktop file. Some examples: Canvas adds 23, FreeHand adds 12, PageMaker adds 10, Microsoft Word adds 20. Also each comment you put in a file’s Get Info box adds 1 resource. On a large disk, it’s easy to exceed the 2727 limit.
Wasted space with small files
Other problems aside, current system software becomes more and more wasteful of space as a volume becomes larger and larger due to large block sizes. For example, on a 300MB volume, every file wastes an average of 2.5K per fork and as much as 10K per file. When you have many small files, this waste can easily exceed the size of the files themselves!
Since today’s disks are often larger than 80MB in size, and some are over 1000MB in size, the number of files on them can easily number in the thousands. Using a single volume on such a disk with lots of small files defeats the purpose of a large disk, since much space is wasted. Of course, if most of your files are significantly larger than the volume block size then the wasted space will not significant.
Combining files together using DiskDoubler's Combine command can eliminate this waste. However, you cannot use a file inside a combined file until you expand the combined file, so we don't recommend this as an everyday working solution.
Partitioning a volume
To avoid the negative aspects of large disks, you can partition a large disk into more than one volume. In general, we recommend that your volumes be no larger than 120MB each. For example, you might partition a 300MB disk into four 75MB volumes or three 100MB volumes, etc. Then you would have several disk icons on your desktop, each of them independent of the others.
Most disk drive manufactures provide software to partition a disk into volumes. Apple’s “HD SC Setup” allows you to partition Apple disks. If your manufacturer does not provide such software, you can buy software to do so, such as LaCie’s SilverLining software.
Apple’s Desktop Manager
Another helpful tool is Apple’s Desktop Manager, which comes with AppleShare, but is available free to anyone who wants to use it. The Desktop Manager eliminates the 2727 resource limit. However, it has no effect on block size of the volume, so space is still wasted on large volumes.
For large disks, we recommend partitioning as the best solution, with the Desktop Manager a useful addition regardless of whether you partition or not.
