![]() ![]() In the "first phase" (with your drive less than half full), it doesn't matter much at all - probably not enough to even make it worth doing. Ultimately this adds up to a situation where you can identify maybe three "phases" of mac life when it comes to the need for defragmentation. Not only this, but things like the "extents files", which record where all the bits are located, will begin to grow astronomically as a result, putting even more pressure on your already stressed drive, and increasing the risk of major failures. The extent of fragmentation of free space at this stage can be simply staggering, and any large files you subsequently write are likely to be divided into many, many tens of thousands of fragments scattered across the drive. The amount of work required to shift the data into contiguous blocks is immense, puts additional stress on the drive, takes forever, etc etc. Eventually the directories and other related files may collapse altogether and they find themselves with a next to unrecoverable disk problems.īy this time, of course, defragging itself has already become just about impossible. Most obviously, though, the computer slows down to a speed not much better than that of molasses. Such users are operating in a zone where they put a lot more stress on their drives as a result, often start complaining of increased "heat", etc etc. On modern large drives by this stage they are usually in fact down to the point where the internal defragmentation routines can no longer operate, where their drives are working like navvies to keep up with finding space for any larger files, together with room for "scratch files", virtual memory, directories etc etc etc. Often you will see that say that "still have 10 or 20 gigs free" or the like. If you look through this discussion board you will see quite a few complaints from people who find that their drive gets "slow". Despite this, the system copes very well without defragging as long as you have plenty of room.Īgain, this doesn't matter much when the drive is half empty or better, but it does when it gets fullish, and it does especially when it gets fullish if you are regularly dealing with large files, like video or serious audio stuff. Eventually, in fact, once the largest free space fragments are down to less than 20 MB (not uncommon on a drive that has, say only 10% free space left) it begins to give up trying to defrag altogether. In fact the method it uses to defrag the smaller files actually increases the extent of free space fragmentation. It doesn't defrag larger files and it doesn't defrag the free space on the drive. ![]() ![]() It defrags files that are less than 20 MB in size. Some people will tell you that "OSX defrags your files anyway". Most users, as long as they leave plenty of free space available, and don't work regularly in situations where very large files are written and rewritten, are unlikely to notice the effects of fragmentation on either their files or on the drives free space much.Īs the drive fills the situations becomes progressively more significant, however. Whilst 'defragging' OS X is rarely necessary, Rod Hagen has produced this excellent analysis of the situation which is worth reading: Aggressive read-ahead and write-behind caching means that minor fragmentation has less effect on perceived system performance.This process is sometimes known as "Hot-File-Adaptive-Clustering." Mac OS X 10.3 onwards can also automatically defragment such slow-growing files. With faster hard drives and better caching, as well as the new application packaging format, many applications simply rewrite the entire file each time. Fragmentation was often caused by continually appending data to existing files, especially with resource forks.This allows a number of small allocations to be combined into a single large allocation in one area of the disk. Mac OS X 10.2 and later includes delayed allocation for Mac OS X Extended-formatted volumes.With more free space available, the file system doesn't need to fill up every "nook and cranny." Mac OS Extended formatting (HFS Plus) avoids reusing space from deleted files as much as possible, to avoid prematurely filling small areas of recently-freed space. Hard disk capacity is generally much greater now than a few years ago.You probably won't need to optimize at all if you use Mac OS X. I would recommend a reinstall from your recovery partition. No such third party utility is required, or even adviseable, on OS X which does such things by itself. IDefrag may well have damaged your system. ![]()
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