{"id":45344,"date":"2024-10-11T15:54:03","date_gmt":"2024-10-11T19:54:03","guid":{"rendered":"https:\/\/mjtsai.com\/blog\/?p=45344"},"modified":"2024-10-11T15:54:03","modified_gmt":"2024-10-11T19:54:03","slug":"a-brief-history-of-defragging","status":"publish","type":"post","link":"https:\/\/mjtsai.com\/blog\/2024\/10\/11\/a-brief-history-of-defragging\/","title":{"rendered":"A Brief History of Defragging"},"content":{"rendered":"

Howard Oakley<\/a>:<\/p>\n

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All storage media, including memory, SSDs and rotating hard disks, can develop fragmentation, but most serious attention has been paid to the problem on hard disks. This is because of their electro-mechanical mechanism for seeking to locations on the spinning platter they use for storage. To read a fragmented file sequentially, the read-write head has to keep physically moving to new positions, which takes time and contributes to ageing of the mechanism and eventual failure. Although solid-state media can have slight overhead accessing disparate storage blocks sequentially, this isn’t thought significant and attempts to address that invariably have greater disadvantages.<\/p>\n

Fragmentation on hard disks comes in three quite distinct forms: file data across most of the storage, file system metadata, and free space. Different strategies and products have been used to tackle each of those, with varying degrees of success.<\/p>\n

[…]<\/p>\n

Manually defragging HFS+ hard disks was always a questionable activity, as Apple added background defragmentation to Mac OS X 10.2, released two years before Coriolis was even founded. By El Capitan and Sierra that built-in defragging was highly effective, and the need for manual defragging had almost certainly become a popular myth.<\/p>\n<\/blockquote>\n

I would agree that defragging became much less useful since the days when I was using the Speed Disk component of Norton Utilities on System 7. But my recollection is that HFS+’s automatic defragmentation didn’t fully solve the problem because it wasn’t able to work on all files (notably skipping large ones, which could have hundreds or even thousands of fragments for a single file) and didn’t consolidate the free space. iDefrag remained useful for spinning disks until the advent of APFS.<\/p>\n

APFS also has built-in defragmentation, which in some cases I enabled myself and in other cases seemed to have been automatically enabled. I haven’t noticed any improvement from enabling it, which is unsurprising since Oakley and Mike Bombich say that it doesn’t defragment the file system metadata. APFS performance remains really bad on spinning disks, in my opinion.<\/p>\n\n

Previously:<\/p>\n