Why there is no option in Apple disk utility to defrag Mac drive. Why there is no need to defragment Mac disk ? The only answer to this question is – Mac OS is smart to minimize the chances of fragmentation.
How does Mac OS handle fragmentation ?
The Mac OS X later than 10.2 have some built-in safeguards to prevent fragmentation of files. Lets see the techniques behind it.
- The HFS+ file system of Mac doesn't allocate the recently freed space to save a file. Instead, it tries to allocate the larger free space first. It reduces the chances of fragmenting the files to make them fit in available space.
- OS X gathers small files and rewrites them into new location on same drive with larger free space. It helps to defrgament all the files in the group.
- Hot file adaptive clustering in Mac OS X is another technique to reduce fragmentation. Here the frequently-accessed files (read only) are moved to a special zone so as to make their access faster.
- Delay in allocating memory to file. The OS X allocates memory in bunches. This reduces chances of saving fragments of a file in separate locations.
These safeguards reduce the level of fragmentation upto very significant extent and that is the reason Apple disk utility doesn't need to offer an extra option to defrag Mac drive. As we know that every technology has some limitations, so is the case with Mac also.
If the size of Mac files exceeds 20 MB , then the OS can take care about fragmentation of that file. In those situations, one needs to defrag the files via some third party tools like Stellar drive defrag.
Also, when the size of free space get lesser than 10% of total size of drive, the OS X can't defrag the files automatically. So, one must keep adequate free space on drive by removing useless applications, unnecessary language files, unwanted universal binaries etc..
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