Hard Drive Fragmentation?

[V6Pony]

I know with OS X you don't have to fragment your hard drive. I was wondering why? If you delete a file I'm sure it creates an open space on the hard drive. When you save a new file does it save into the open space. Looks like that would cause the file to be spread in different locations. Causing longer seek times?

 

[Lifeisabeach]

I know with OS X you don't have to fragment your hard drive. I was wondering why? If you delete a file I'm sure it creates an open space on the hard drive. When you save a new file does it save into the open space. Looks like that would cause the file to be spread in different locations. Causing longer seek times?

I imagine in your first line, you meant "I know with OS X you don't have to defragment your hard drive". That is a myth, or at least in part. It is true that OS X will automatically defragment very small files, but doesn't for larger files and doesn't do so at all in an "optimal" manner. Whether or not one NEEDS to do more than what OS X does do is dependent on what you typically do on your Mac. If you have a lot of media files or work with software like Photoshop, you will benefit. Here's a post on Apple's forums that does a great job of summarizing it:
How to safely defrag a Mac's hard drive: Apple Support Communities

 

[V6Pony]

Thanks lifeisabeach. Just what I was looking for.

 

[Lifeisabeach]

Thanks lifeisabeach. Just what I was looking for.

No problem. If you do a forum search, you'll find other posts about it. Most of the regulars here believed at one time that defragging was unnecessary, but most have come around on that. I have a couple posts about it, one demonstrating measurable improvements in boot times. In another instance, I was having trouble streaming videos and defragging helped fix that.

BTW, if you decide you do need/want to defrag, I heartily recommend iDefrag. It seems to be the best at this.

 

[pigoo3]

In case anyone is interested in more info on iDefrag...here's a review on it:

http://reviews.cnet.com/8301-13727_7-10422120-263.html

As lifeisabeach mentioned (and so does the iDefreg review)...Mac OS X automatically defrag's smaller files (under 20meg's) but does not defrag. larger files.

If someone regularly works with a lot of files larger than 20meg...iDefrag might be a good thing to run very now & then.

- Nick

 

[bobtomay]

Another believer in iDefrag here.

I've found it can make a noticeable difference in speed when I start hitting 30-40% "used" space - have to know I can have a lot more than that move on and off a drive.

While I use it regularly on my HDs, my wifes 6+ yr old MB has never been defragged - I think she's down to maybe 75% free space now and I doubt anything she installs/downloads ever gets deleted.


edit:
See below - don't defrag your SSD.

 

[RadDave]

Well after looking at the two excellent links and reviewing the posts, there are a number of us w/ fairly new Macs (for myself iMac & MBPro, both 6 months old) and also w/ SSD technology - i.e. MBPro 256 GB SSD & iMac w/ a Fusion HD - wife & I really do not work w/ huge files (i.e. at 20+ MBs), so what would be the advice on defrag?

I was involved in another thread here which suggested that a SSD should not be subjected to defragmentation - would appreciate further comments and I'm sure others in this situation would be helped - thanks. Dave

 

[chscag]

Never, repeat, never defrag a SSD. Only spinning hard drives should be subjected to a defrag.

 

[RadDave]

Never, repeat, never defrag a SSD. Only spinning hard drives should be subjected to a defrag.

Thanks Chscag - that was my 'take away' message from the previous thread mentioned, i.e. no defrag needed on my SSD MBPro; now the 'fusion' drive on our new iMac is 1TB w/ 128 GB SSD (believe that is right) - should defrag be done on the latter?

Just bringing this SSD option into this discussion (whether partial or complete) because many newer members are buying into this technology and as the prices drop on 'flash SS storage' , the need for defragmentation will start to disappear - Dave

 

[chscag]

I wouldn't attempt to defrag the fusion drive either because when joined together (Apple design) the spinning drive and the SSD are one.

 

[Slydude]

Good point Charlie. I had not thought of that as an issue.

 

[V6Pony]

Well I have a Seagate ST750LX003 Hybrid that has some ssd drive but mostly standard HD. I'm guessing from the above that I should not defrag this drive as well?

 

[chscag]

Yes, the same holds true for hybrid drives although they're somewhat different from the Apple designed fusion drive.

 

[AndyClift]

Just a thought. When I have restored my boot drive from my Time Machine backup it first formats the drive. I guess that it then restores file by file so that would also defrag the drive

 

[bobtomay]

Yes, a format, then clean install and restore or cloning your drive from your SD! or CCC backup does essentially the same thing as far as getting your data back on the front of the drive and getting your free space back to a contiguous chunk rather than spread out all over the drive.

The SSD standard wisdom comes from them having a limited number of writes prior to failure.
How many years to expect an SSD to last - that jury is still out and how defragging would affect that life span has not been tested.

There has not been much testing of defragging SSDs at all, but one of the PCWorld writers did some experimentation earlier this month and can be found here. Although, wish he had stated how much space had been used vs free on the drive.

The reports are that SSDs "do" slow down as they become full. At what percentage of free space that happens to begin, don't have a clue and I've not seen suggestions on how much free space to maintain in any of the articles I've read.

I'm still on my first SSD and at only 256 GB, I knew going in that it could not be used for storage of even a percentage of my data. So two years later, and while I'd guess perhaps 1 TB or more has moved on and off the drive, I'm just now hitting 50% used space and still not really "noticing" a slow down the way I have on every HD I've ever owned.

Games like WoW and CoD 2 still play adequately well and just doing a check with iDefrag - still have at least 30-35% of the drive shown as free contiguous space. Don't use this machine for video encoding so can't give a comparison there.

 

[Lifeisabeach]

Just a thought. When I have restored my boot drive from my Time Machine backup it first formats the drive. I guess that it then restores file by file so that would also defrag the drive

That is a crude way of doing it, and restoring a clone of the drive using Carbon Copy Cloner or SuperDuper has often been recommended here and around the web as a cheap and easy defrag. However, it doesn't do this in an "intelligent" manner like a good defragger can. It's also worth pointing out that even the developers of SuperDuper recommend iDefrag if you want to do it right, though I would suggest that's really more important for people whose use scenarios would best benefit from it as previously described.
http://s3.amazonaws.com/com.shirtpocket/SuperDuper/Fragmentation.pdf

 

[bobtomay]

That is a crude way of doing it, and restoring a clone of the drive using Carbon Copy Cloner or SuperDuper has often been recommended here and around the web as a cheap and easy defrag. However, it doesn't do this in an "intelligent" manner like a good defragger can. It's also worth pointing out that even the developers of SuperDuper recommend iDefrag if you want to do it right, though I would suggest that's really more important for people whose use scenarios would best benefit from it as previously described.
...

Agreed.

I would suggest that method only for those too cheap to pay for the right tool for the job, although, it will give you back your contiguous free space.

I can tell you based on my own experimentation when using SD! to clone new drives - running iDefrag on those newly cloned drives has resulted in boot times being reduced by a good 20% average.