Myths
Defragging the disk will not stop a system from malfunctioning or crashing because the filesystem is designed to work with fragmented files. [2] Since defrag cannot be run on a filesystem marked as dirty without first running chkdsk [3], a user who intends to run defrag "to fix a system acting strangely" often ends up running chkdsk, which repairs file system errors, the end result of which may mislead the user into thinking that defrag fixed the problem when it was actually fixed by chkdsk.
In fact, in a modern multi-user operating system, an ordinary user cannot defragment the system disks since superuser access is required to move system files. Additionally, modern file systems such as NTFS are designed to decrease the likelihood of fragmentation. [4] Improvements in modern hard drives such as RAM cache, faster platter rotation speed, and greater data density reduce the negative impact of fragmentation on system performance to some degree, though increases in commonly used data quantities offset those benefits. However, modern systems profit enormously from the huge disk capacities currently available, since partially filled disks fragment much less than full disks. [5] In any case, these limitations of defragmentation have led to design decisions in modern operating systems like Windows Vista to automatically defragment in a background process but not to attempt to defragment a volume 100% because doing so would only produce negligible performance gains. [6]
Defragging the disk will not stop a system from malfunctioning or crashing because the filesystem is designed to work with fragmented files. [2] Since defrag cannot be run on a filesystem marked as dirty without first running chkdsk [3], a user who intends to run defrag "to fix a system acting strangely" often ends up running chkdsk, which repairs file system errors, the end result of which may mislead the user into thinking that defrag fixed the problem when it was actually fixed by chkdsk.
In fact, in a modern multi-user operating system, an ordinary user cannot defragment the system disks since superuser access is required to move system files. Additionally, modern file systems such as NTFS are designed to decrease the likelihood of fragmentation. [4] Improvements in modern hard drives such as RAM cache, faster platter rotation speed, and greater data density reduce the negative impact of fragmentation on system performance to some degree, though increases in commonly used data quantities offset those benefits. However, modern systems profit enormously from the huge disk capacities currently available, since partially filled disks fragment much less than full disks. [5] In any case, these limitations of defragmentation have led to design decisions in modern operating systems like Windows Vista to automatically defragment in a background process but not to attempt to defragment a volume 100% because doing so would only produce negligible performance gains. [6]
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