Defragmenting macOS volumes: how to do it and is it necessary?

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Defragmenting macOS volumes: how to do it and is it necessary?

Hello folks,

I've seen lots of articles on many sites discussing defragmenting disks. I have a few questions:

Is it necessary to do it? Some articles say "yes" and some say "no" (but the explanations leave me skeptical).
If so, does macOS have a built-in utility to defrag disks?

I am hot on this topic again because I've noticed that Time Machine back ups really seem to progress with a wide variability in backup progress. It's chugging along and sometimes goes at 20MB/sec but then will enter a period during backup at some ungodly slow 10KB/sec for several minutes at a time.

I don't know why, but I'm wondering if either my main Macintosh HD or the external backup drive is highly fragmented.

Thanks in advance,

Posted on Dec 18, 2019 10:20 PM

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Answer 1

Best reply

Rudegar

Level 10

171,078 points

Dec 18, 2019 10:43 PM in response to vxiansheng

you don't need to read

https://www.macworld.co.uk/how-to/mac/defrag-3600241/

https://www.lifewire.com/need-to-defragment-mac-hard-drive-2260194

more

https://www.google.com/search?q=defragmenting+macOS&oq=defragmenting+macOS&aqs=chrome..69i57j69i61j0l5.2331j0j7&sourceid=chrome&ie=UTF-8

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Answer 2

Dec 18, 2019 10:51 PM in response to vxiansheng

vxiansheng wrote:

1. Hello folks,

I've seen lots of articles on many sites discussing defragmenting disks. I have a few questions:

Is it necessary to do it? Some articles say "yes" and some say "no" (but the explanations leave me skeptical).

2. If so, does macOS have a built-in utility to defrag disks?

I am hot on this topic again because I've noticed that Time Machine back ups really seem to progress with a wide variability in backup progress. It's chugging along and sometimes goes at 20MB/sec but then will enter a period during backup at some ungodly slow 10KB/sec for several minutes at a time.

I don't know why, but I'm wondering if either my main Macintosh HD or the external backup drive is highly fragmented.

Thanks in advance,

I would not try and second guess Time Machine— that is no kind of indicator.

I have cloned my internal SSD drive to an external, and then back again—consequence regaining storage space.

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Answer 3

Dec 19, 2019 10:05 AM in response to vxiansheng

There are a whole variety of factors involved when it

comes to Time Machine backups and how long they

take from what it is backing up (especially if there are

a lot of small files), what else is running on the system

at the time it is backing up, what disk activity

is taking place at the time of backup, etc., etc. There is also

a lot of bookkeeping that needs to take place as well in order

to keep it all straight.

So, can the back up rates vary, yes by quite a bit at times.

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Answer 4

vxiansheng Author

Level 1

19 points

Dec 19, 2019 1:17 PM in response to vxiansheng

Thanks for all the replies. Yeah, I read most of those articles and many others. I guess the upshot is that it is difficult to understand the algorithms used when viewing behavior from the outside. Two of the articles referenced (as well as many others I've read over the past two macOS releases) indicate that you do need to defrag sometimes. Naturally, nothing is perfect so I am not surprised.

Playing around with "du", "df -i" and "ls -il" perplexed me even more... thus my original post. I have been seeing such wide variability in my Time Machine backups that I wondered if my system was not at the point of "one of those times" when I should defrag.

I know that there is a lot going on, Spotlight indexing files, etc. but monitoring processes does not show high CPU or disk activity when I noticed really, really slow backup performance. I mean, the variability goes from "Activity Monitor" and "iostat" showing 20 MB/sec write speed to 3 KB/sec write speed and not any appreciable read rates. At those times CPU usage is nominal (less than 30% at most). So, naturally, I considered everything. :-)

So... I will start with a restore from TimeMachine as I do include system files and applications... my backups are bootable images.

Many sincere thanks or the replies....

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Defragmenting macOS volumes: how to do it and is it necessary?

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