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ktalebian

macrumors regular
Original poster
Dec 25, 2007
214
0
Hi there
I want to run a full defrag. Can I use the CDs that came with Mac to boot the system from them and run the defrag? Or do i need to make a boot cd another way?

Thanks!
 

MisterMe

macrumors G4
Jul 17, 2002
10,709
65
USA
... I want to run a full defrag. ...
You are wasting your money and wasting your time. It can actually do more harm than good. Defragging is a Windows solution to a Windows problem. Apple explicitly recommends that Mac users not do it. MacOS X defrags automatically.
 

tersono

macrumors 68000
Jan 18, 2005
1,999
1
UK
Hi there
I want to run a full defrag. Can I use the CDs that came with Mac to boot the system from them and run the defrag? Or do i need to make a boot cd another way?

Thanks!

You ARE aware that OS X does file-level defragmentation on the fly, yes?
You are also aware that a full defrag will actually slow down your system as it's far slower to read data from a single contiguous area on an HD rather than from several areas/platters simultaneously, yes?

There are a very small number of reasons why a defrag can sometimes be a good idea on a *nix operating system, but these are few and far between (mostly involving editing large video or audio files on a partition containing other data - although even then, a dedicated volume is a much better idea). Most people would be far better advised to leave well alone.
 

Nubben

macrumors regular
Mar 17, 2005
147
6
All of you are wrong.

1. Mac OS X only defrags files below the 20MB level.

2. How can reading a file that's scattared on a HD be faster than reading from one single defragged file? Simply not true. The drive head has to move constantly to different parts of the disk.

3. Apple doesn't explicitly say EITHER that defragging should NOT be done. It's probably because the large part of Mac users - read regular users - do not have large files that are bigger than 20MB.

4. Genius Bars use on a regular basis Disk Rescue and Drive Genius (defragger) to optimise the drives. They used those on my Mac when I handed mine in for its yearly check-up.

So, defragging is only useful if you have plenty of large files (above 20MB).
 

iSamurai

macrumors 65816
Nov 9, 2007
1,023
1
ɹǝpun uʍop 'ǝuɐqsı&#
You are also aware that a full defrag will actually slow down your system as it's far slower to read data from a single contiguous area on an HD rather than from several areas/platters simultaneously, yes?

2. How can reading a file that's scattared on a HD be faster than reading from one single defragged file? Simply not true. The drive head has to move constantly to different parts of the disk.

yeah, I thought this was weird. obviously the drive head has to move around the disk to search for pieces of a file... this will be slower than a chunk of data on a same sector.
 

ElectricSheep

macrumors 6502
Feb 18, 2004
498
3
Wilmington, DE
KB Note 25668:

You probably won't need to optimize at all if you use Mac OS X. Here's why:
Hard disk capacity is generally much greater now than a few years ago. 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.

Mac OS X 10.2 and later includes delayed allocation for Mac OS X Extended-formatted volumes. This allows a number of small allocations to be combined into a single large allocation in one area of the disk.

Fragmentation was often caused by continually appending data to existing files, especially with resource forks. With faster hard drives and better caching, as well as the new application packaging format, many applications simply rewrite the entire file each time. Mac OS X 10.3 Panther can also automatically defragment such slow-growing files. This process is sometimes known as "Hot-File-Adaptive-Clustering."

Aggressive read-ahead and write-behind caching means that minor fragmentation has less effect on perceived system performance.

For these reasons, there is little benefit to defragmenting.

Note:Mac OS X systems use hundreds of thousands of small files, many of which are rarely accessed. Optimizing them can be a major effort for very little practical gain. There is also a chance that one of the files placed in the "hot band" for rapid reads during system startup might be moved during defragmentation, which would decrease performance.
 

err404

macrumors 68030
Mar 4, 2007
2,524
624
What about a FAT32 disk? Is there a tool for OS X to defrag a USB drive formatted in FAT32? I ask because I have an old device that uses SD cards and it has issues with files fragmented into more than 32 chunks. I have to break out my old Windows laptop every once and a while just to do the defrag...
 

err404

macrumors 68030
Mar 4, 2007
2,524
624
This whole thread is FUD against MS. I don't see anything on Apple's site telling you not to defragment HSF+. They only say you 'shouldn't' need to. The article on the subject even recommends four third party tools for it.

Apple's support site About disk optimization with Mac OS X said:
"If your disks are almost full, and you often modify or create large files, there's a chance the disks could be fragmented. In this case, you might benefit from defragmentation, which can be performed with some third-party disk utilities.

Another option is to back up your important files, erase the hard disk, then reinstall Mac OS X and your backed up files.
:eek:


I realize that HFS+ is less prone to severe fragmentaion then NTFS, but frankly an NTFS disk with a lot of free space and few large files will never need to be defragmented either. At least MS includes the tool if it occurs.
 

Plusbits

macrumors member
May 4, 2008
60
0
Birmingham, UK
Uh. No.

lol

Actually, you are. If the read head is going to constantly be scanning the drive and across platters for a string of data, of course it's going too be faster for it to read if it's in a continuous string, not spread out across the drive. Especially if it's a larger capacity drive that's almost full. There have also been instances where drives have become so fragmented that they won't even boot. Seriously, do your homework before you shoot your mouth off
 

portent

macrumors 6502a
Feb 17, 2004
623
2
Actually, you are. If the read head is going to constantly be scanning the drive and across platters for a string of data, of course it's going too be faster for it to read if it's in a continuous string, not spread out across the drive. Especially if it's a larger capacity drive that's almost full. There have also been instances where drives have become so fragmented that they won't even boot. Seriously, do your homework before you shoot your mouth off

Take your own advice there.

Firstly, Mac OS X does its own optimization of system files. Moving them around with the intention of putting them in neat, pretty little rows may seem like a good idea, but it can actually destroy the ordering of these files.

Second, files are not static things. Oftentimes, existing files need to be modified. On a just-defragged disk, all the files are bunched up together with no room to grow. Adding data to any file means the entire file has to be duplicated somewhere else or (you guessed it) fragmented, whereas "fragmented" disks often have plenty of "in between" space all around the disk.

The idea of defragmenting files into neat little rows appeals to the obsessive-compulsive mind, but usually is just a waste of time on modern systems.
 

jb60606

macrumors 6502a
Jan 27, 2008
871
0
Chicago
There is a defragmenter included in the "TechTools" application (on the AppleCare CD). I don't think you need to worry about using it if you have an abundance of free space, though. OSs will only fragment the file if it can't find contiguous space large enough to plant the entire thing.
 

Plusbits

macrumors member
May 4, 2008
60
0
Birmingham, UK
Take your own advice there.

Firstly, Mac OS X does its own optimization of system files. Moving them around with the intention of putting them in neat, pretty little rows may seem like a good idea, but it can actually destroy the ordering of these files.

Second, files are not static things. Oftentimes, existing files need to be modified. On a just-defragged disk, all the files are bunched up together with no room to grow. Adding data to any file means the entire file has to be duplicated somewhere else or (you guessed it) fragmented, whereas "fragmented" disks often have plenty of "in between" space all around the disk.

The idea of defragmenting files into neat little rows appeals to the obsessive-compulsive mind, but usually is just a waste of time on modern systems.

Firstly, I never said anything about defragging on a Mac, I'm aware that it can mess with the system, I was merely referring to the idea as a whole, primarily on MS machines. Should've mentioned that, so I appologise for that mistake

Secondly, that's just more reason to defrag often. Having a drive full of defragmented files is a hell of a lot worse than some defragmented some not. Granted, if you defrag a drive and then don't do so again for a long time it's going to make it slower, but as long as you keep on top of it, even schedualing a background defrag, it'll keep the drive healthier

A perfect example is Steam releasing a defragger for Half Life 2, because it was running stupidly slow and crashing for some people due to, you guessed it, fragmented files
 

err404

macrumors 68030
Mar 4, 2007
2,524
624
The idea of defragmenting files into neat little rows appeals to the obsessive-compulsive mind, but usually is just a waste of time on modern systems.

I partially agree that both NTFS and HSF+ are fairly resistant to fragmentation so long as a reasonable amount of the disk remains free, but you don't seem to have a very good understanding of disk fragmentation. I want to point out that compacting data into 'neat little rows' is not that same a defragmentation. Defragmentation is just the reordering of files pieces into a contiguous block. A good defrag tool will not compact all of the files to the beginning of your disk, but rather leave space between files. Even the basic Windows tool leaves this space. A good defrag tool will also order files on your drive according to usage statistics to group related files together (Both Windows and OS X do this automatically w/o the need for an actual defrag). There is literally no modern defrag tool that will 'destroy the ordering of files', but even if it did, the effect would be minimal since OS X employs aggressive read buffers to minimize parallel IO seeks. Disk head travel due to fragmentation is much worse than file ordering since there is no method to read an entire file faster if you have parts all over he disk, each requiring an addition head seek.

The fact is HFS+ does fragment over time and for files over 20mb, there is nothing built into the OS to fix it (outside of Apple's recommendation to format your disk and start over)

That all said, I don't bother with defrags.
BTW - In my job, I monitor a few thousand windows servers. For servers that maintain at least 20% free space, a defrag is NEVER needed. But when you push that limit, watch out, that disk is going to need some work soon.
 

Ploki

macrumors 601
Jan 21, 2008
4,242
1,501
i defragged my drive :)
cant say that it affects normal use.
logic pro however... ;)
 

OldCorpse

macrumors 68000
Dec 7, 2005
1,634
212
compost heap
Anecdotal evidence here from real life... I defragged my mac mini several times using iDefrag (an app from a company that is very respected). I never noticed any speedup of my system - in fact, I am quite certain that it SLOWED it down (Tiger 10.4.9). Finally, after one defragg, my HDD croaked - I don't know if it was connected with iDefrag, but I've read several reports to the effect that it can kill your HDD, and it happened to me (the only time ever I got a dead HDD)... maybe it was coincidence, maybe not. Bottom line: I'm staying away. No benefit, possible harm. YMMV.
 

err404

macrumors 68030
Mar 4, 2007
2,524
624
@OldCorpse - Defragging a drive is a very intensive process that can push a failing disk over the edge, but assuming your disk is free of any pre-existing defects, you should be fine. If it failed on a defrag, it was probably on it's last leg all ready.
 
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