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[ The PC Guide | Systems and Components Reference Guide | Hard Disk Drives | Hard Disk Logical Structures and File Systems | Partitioning, Partition Sizes and Drive Lettering ]

Partition Size Tradeoff: Slack Waste and "End of Volume" Space Waste

One sensible way to combat the large amount of wasted slack space that results from the use of large cluster sizes, is to split larger hard disks into multiple smaller partitions. I discussed this in some detail here. Using partitioning to reduce slack is pretty much a necessity if your operating system does not support FAT32, and with very large hard disks it is also commonly done even with FAT32, to keep cluster sizes to a reasonable level and ensure reasonably efficient utilization of the hard disk.

Unfortunately, there are some people who don't understand the concept called "too much of a good thing". They tend to go overboard and chop their hard disks into ridiculous numbers of tiny partitions, thinking that they are maximizing their use of disk space this way. The ironic thing is that, in addition to making life confusing for themselves (was that file on F:? Or was it I:?) they end up not saving nearly as much space as they thought they would. The reason is that the smaller a disk volume is, the larger a percentage of it has to be left empty in order to avoid the possibility of running out of disk space. Running out of disk space can lead to data loss, and letting a hard disk get close to the point where it is running out of space can result in increased fragmentation and performance degradation if you are doing a lot of work on the disk. I call space that is reserved to ensure that volumes don't run out of space end of volume space.

Generally speaking, most people have a "comfort zone" regarding how little disk space they feel comfortable with having on a disk. If the amount of free space gets below this amount, they will tend to want to find something to delete, or if they are able to, get more storage. The problem is that if you have oodles of tiny partitions, it is very easy to run out of space on one while having another half empty. This situation is far more common when chopping up partitions under FAT16, because if you have a hard disk that needs partitioning for efficiency under FAT32, it's pretty large. But at the same time, FAT32 systems tend to have much larger files overall too.

Let's suppose that our comfort factor for free space at the end of a volume is 20 MiB. (For me, this is way too low. I get nervous if a regular volume ever gets below about 50 MiB, and now that I am using much bigger disks and files I really like to have 500 MiB free if at all possible!) Now, let's re-examine the same 2 GiB disk with 24,000 files that we looked at in the discussion of partitioning, only this time also looking at the end of volume space, assuming 20 MiB per partition for this:

Cluster Size

Size of Each Partition

Number of Partitions

Typical Total Slack (All Partitions)

Total End of Volume Space

Sum of Slack and End of Volume Space

2 kiB

128 MiB

16

28 MiB

320 MiB

336 MiB

4 kiB

256 MiB

8

56 MiB

160 MiB

216 MiB

8 kiB

512 MiB

4

112 MiB

80 MiB

192 MiB

16 kiB

1 GiB

2

225 MiB

40 MiB

265 MiB

32 kiB

2 GiB

1

450 MiB

20 MiB

470 MiB

The answer to the question of efficiency isn't so clear-cut now, is it? I mean, the 32 kiB cluster size option is still ridiculous, but really, so is the 2 kiB cluster size option. Even if you use 8 partitions with 4 kiB clusters, you'll be wasting a lot of space at the end of each volume. In a FAT32 system with a large hard disk you have the same general issue, but it's less of a concern, because each partition is so much larger. If you have a 64 GiB hard disk and chop it into eight 8 GiB partitions then you will need to "save space" at the end of each partition, but each partition is pretty big. Then again, if you are using these partitions to store much larger files than you did under FAT16 (which often happens) then you are back in the same place again anyway.

The matter of "end of volume" space is one reason why I personally believe in not using excessive numbers of partitions. The other is simply that I get tired of always trying to figure out where my stuff is when I have to look through 8 or 10 partitions for it. I think fewer partitions keep the disk better organized than more partitions do.

Next: Do More Partitions Keep the Disk "Organized"?


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