Frequently Asked Question

Do you mean is it necessary to have multiple partitions?

No, neither on an SSD or a HD.

Here's an article I wrote on the subject a while back:

Planning Your Partitions
*The Question*
How many partitions should I have on my hard drive, what should I use each one for, and how big should each of them be?
It’s a common question, but unfortunately one that doesn’t have a single simple answer, right for everyone. Many people will answer with the way they do it, but their answer isn’t necessarily best for the person asking (in many cases it isn’t even right for the person responding).
*The Terminology*
First, let’s get the terminology right. Some people ask “should I partition my drive?” That’s the wrong question, because the terminology is a little strange. Some people think that the verb “partition” means to divide the drive into two or more partitions. That’s not correct: to partition a drive is to create one or more partitions on it. You have to have at least one partition on it to use it. Those people who think they have an unpartitioned drive actually have a drive with only a single partition on it, and it’s normally called C:. The choice you have is whether to have more than one partition, not whether to partition at all.
*Some History*
Back before Windows 95 OEM Service Release 2 (also known as Windows 95B) was released in 1996, all MS-DOS and Windows hard drives were set up using the FAT16 file system (except for very tiny ones using FAT12). Because only 16 bits were used for addressing, FAT16 has a maximum partition size of 2Gb.
Hard drives larger than 2GB were rare in those days, but if you had one, you had to have multiple partitions to use all the available space. But even if your drive was no bigger than 2GB, FAT16 created another severe problem for many people–the size of the cluster was bigger if you had a bigger partition. Cluster sizes went from 512 bytes for a partition no bigger than32Mb all the way up to 32Kb for a partition of 1Gb or greater.
The larger the cluster size, the more space is wasted on a hard drive. That’s because space for all files is allocated in whole clusters only. If you have 32Kb clusters, a 1-byte files takes 32Kb, a file one byte larger than 32Kb takes 64Kb, and so on. On the average, each file wastes about half of its last cluster.
So large partitions create a lot of waste (called “slack”). With a 2GB FAT16 drive in a single cluster, if you have 10,000 files, each wasting half of a 32Kb cluster, you waste about 160Mb to slack. That’s a substantial portion of a drive that probably cost over $400 back in 1996–around $32 worth.
So what did people do? They partitioned their 2GB drive into two, three, or more logical drives. Each of those logical drives was smaller than the real physical drive, had smaller clusters, and therefore less waste. If, for example, they could keep all partitions under 512Mb, cluster size was only 8Kb, and the waste was reduced to a quarter of what it would otherwise be.
People partitioned for other reasons too, but back in the days of FAT16, this was the main reason for doing so.
*The Present*
Three things have changed dramatically since 1996:
1. The FAT32 and NTFS file systems have come along, permitting larger partitions with smaller clusters, and therefore much less waste. In fact, with NTFS, cluster sizes are 4K, regardless of partition size.
2. Hard drives have become much bigger, often over 1Tb (1000Gb) in size.
3. Hard drives have become much cheaper. For example, a 500Gb drive can be bought today for around $50. That’s 250 times the size of that typical 2Gb 1996 drive, at about an eighth of the price.
What those things mean together is that the old rationale of having multiple partitions to avoid substantial waste of disk space is gone. The amount of waste is much less than it used to be and the cost of that waste is much less. For all practical purposes, almost nobody should be concerned about slack anymore, and it should no longer be considered when planning your partition structure.
*What Partitions are Used for Today*
There is a wide variety of different ways people set up multiple partitions these days. Some of these uses are reasonable, some are questionable, some are outright bad. I’ll discuss a number of common partition types in what follows:
1. A partition for just Windows
Most people who create such a partition do so because they believe that if they ever have to reinstall Windows cleanly, at least they won’t lose their data and won’t have to reinstall their applications, because both are safe on other partitions.
In fact the first of those thoughts is a false comfort, and the second is downright wrong. See the discussion of partition types 2 and 4 below to find out why.
Also note that as time passes, many people find that their Windows partition that started out to be the right size turns out to be too small. For example, if you have such a Windows partition, and later upgrade to a newer version of Windows, you may find that your Windows partition is too small.
2. A partition for installed programs
This normally goes hand-in-hand with partition type 1, a partition for just Windows. The thought that if you reinstall Windows, your installed application programs are safe if they are in a separate partitions is simply wrong. That’s because all installed programs (except for an occasional trivial one) have pointers to them within Windows, in the registry and elsewhere, as well as associated files buried within the Windows folder. So if Windows goes, the pointers and files go with it. Since programs have to be reinstalled if Windows does, this rationale for a separate partition for programs doesn't work. In fact, there is hardly ever a good reason for separating Windows from application software in separate partitions.
3. A partition for the page file.
Some people erroneously think that having the page file on a separate partition will improve performance. That is also false; it doesn’t help, and often hurts, performance, because it increases head movement to get back and forth from the page file to the other frequently-used data on thedrive. For best performance, the page file should normally be on the most-used partition of the least-used physical drive. For almost everyone with a single physical drive, that’s the same drive Windows is on, C:.
4. A partition for backup of other partitions.
Some people make a separate partition to store backups of their other partition(s). People who rely on such a "backup" are just kidding themselves. It's only very slightly better than no backup at all, because it leaves you susceptible to simultaneous loss of the original and backup to many of the most common dangers: head crashes and other kinds of drive failure, severe power glitches, nearby lightning strikes, virus attacks, even theft of the computer. In my view,secure backup needs to be on removable media, and not kept in the computer.
5. A partition for data files
Above, when I discussed separating Windows on a partition of its own, I pointed out that separating data from Windows is a false comfort if it’s done with the thought that the data will be safe if Windows ever has to be reinstalled. The reason I call it a false comfort is because I fear that many people will rely on that separation, think that their data is safe there, and therefore do not take appropriate steps to back it up. In truth the data is not safe there. Having to reinstall Windows is only one of the dangers to someone’s hard drive, and not even the most likely one. This kind of “safeguard” falls into the same category as a partition for backup of other partitions; it leaves you susceptible to simultaneous loss of the original and backup to many of the most common dangers that affect the entire physical drive, not just the particular partition. Safety comes from a strong backup regimen, not from how you partition.
However for some people it can be a good idea to separate Windows and programs on the one hand from data on the other, putting each of the two types into separate partitions. I think that most people’s partitioning scheme should be based on their backup scheme, and backup schemes generally fall into two types: imaging the entire hard drive or backup of data only. If you backup data only, that backup is usually facilitated by having a separate partition with data only; that permits backing up just that partition easily, without having to collect bits and pieces from here and there. On the other hand, for those who backup by creating an image of the entire drive, there is usually little, if any, benefit to separating data in a partition of its own.
By the way, in all fairness, I should point out that there are many well-respected people who recommend a separate partition for Windows, regardless of your backup scheme. Their arguments haven’t convinced me, but there are clearly two different views here.
6. A partition for picture files
Some people like to treat pictures and videos as something separate from other data files, and create a separate partition for them. To my mind, a picture is simply another kind of data, and there is no advantage in doing this.
7. A partition for music files.
The comments above pertaining to picture files apply equally to music files. They are just another kind of data and should be treated the same way as other data.
8. A partition for a second operating system to dual-boot to.
For those who run multiple operating systems (Windows Vista, Windows XP, Windows 98, Linux, etc.), a separate partition for each operating system is essential. The issues here are beyond the scope of this article, but it’s sufficient to note that I have no objection at all to such partitions
*Performance*
Some people have multiple partitions because they believe that it somehow improves performance. That’s not correct. The effect is probably small on modern computers with modern hard drives, but if anything, the opposite is true: more partitions mean poorer performance. That’s because normally no partition is full and there are therefore gaps between them. It takes time for the drive’s read/write heads to traverse those gaps. The closer together files are, the faster access to them will be.
*Organization*
I think many people overpartition because they use partitions as an organizational structure. They have a strong sense of order and want to separate apples from oranges on their drives.Yes, separating different kinds of files on partitions is an organizational technique, but so is separating different kinds of files in folders. The difference is that partitions are static and fixed in size, while folders are dynamic, changing size automatically as necessary to meet your changing needs. That generally makes folders a much better way to organize, in my view.True, partitions can be resized when necessary, but except for newer versions of Windows, doing so requires third-party software (and the ability to do it in Windows is primitive, compared to the third-party solutions). Such third-party software normally costs money, and, no matter how good and how stable it is, affects the entire drive, entailing a risk of losing everything. Plan your partitions well in the first place, and no repartitioning should be necessary. The need to repartition usually comes about as a result of overpartitioning in the first place.

What frequently happens when people organize with partitions instead of folders is that they miscalculate how much room they need on each such partition, and then when they run out of room on the partition where a file logically belongs, while still having lots of space left on the other, they simply store the file in the "wrong" partition. Paradoxically, therefore, that kind of partition structure results in less organization rather than more.


*So How Should I Partition My Drive*
If you've read what came before, my conclusions won't come as a surprise:
1. if your backup scheme is to image the entire drive, have just a single partition (usually C:);
2. if you just backup data, have two partitions–one for Windows and installed application programs (usually C:), the other for data (usually D:).
Except for those running multiple operating systems, there is seldom any benefit to having more than two partitions.