View Full Version : Scan Disk And Defragment? Software?

22nd February 2004, 03:29 AM
Iím kind of new to Macís
What would be one of the better Disk Defragmenter and scan disk programs out there for a mac?

I know for a PC Diskeeper is #1 for 2000, XP or any NT system but whatís hot for Macs?

By the way, doses the 9.2.2 mac OS even have a good built in disk scan utility to correct file structure errors and scan bad clusters like the windows one?

22nd February 2004, 11:50 AM
Are you running X or 9?

Norton system utils and Disk Warrior seem to be the best.

'fsck' is bulit in to OSX, for basic file structure and permission repairs.

22nd February 2004, 12:29 PM
Norton Systemworks 3. Comes with an entirely self-contained bootable CD.

22nd February 2004, 01:44 PM
Yes, itís 9.2.2

You know I found some other posts on some other boards about this; it seems a lot of people are saying that the file structure of a mac is so efficient that you donít even need a disk defragmenter unless youíre doing video editing; you guys have any opinion on that?

22nd February 2004, 02:35 PM
OK, here are the facts about disk defragmentation and Norton Utilities:

First, Symantec's tools really rot on OS X. They are not trustworthy at this time. Maybe, perhaps, they'll get their act together and come out with something that does not destroy OS X but presently they should only be used for OS 9. I can recommend Alsoft's Disk Warrior (http://alsoft.com/DiskWarrior/) which does work with OS X.

One of the wonderful things that Symantec's Norton Utilities used to do under OS 9 (Am I showing my age yet?) is it would give you this cool color-coded graph of how it would optimize the drive, placing all of the programs in one spot, all data at the end, close to where you would add new data. According to the folks at Symantec, this would make your hard disk faster.

Yeah, right.

Here is where my opinion diverges from those of the good folks at Norton. Their opinion may have held with older, slower hard disks and with an older operating system that was not as capable of housekeeping as is Unix (which is what you are running under Jaguar or Panther) but it does not hold today.

If you truly want a good high-speed hard disk (which is why you would want to defragment the one you have), get a big one one with a nice big RAM cache. I have a Western Digital 100Gbyte drive with an 8 Megabyte RAM cache built onto the drive. I can detect no speed difference whether or not I turn on journaling. It is my primary boot drive. Runs great. I shall replace it before it gets three years old with a larger drive that is even faster.

I have several other drives that I use for media. And I don't optimize them either. What I do is, when I am done with a project, I back up what is necessary and reformat the drive. Boom! Totally optimized for the next assault. Any media that I need to have handy goes onto a DVD or CD disk and I can restore it from there.

My media drives are set up for just media. Anything I put on them is supposed to be deleted after the project is done. That kind of stuff can get pretty fragmented if I am doing lots of effects but that is why I generally replace media drives after one or two years. They're going to get harder use.

Here is how I have increasingly started to manage hard disk space:

My boot drive contains my UNIX kernal and all applications, as well as user space. I have aliased the data file folders that I use regularly, so under ~/Documents/ i have an alias to a folder called /Files/

/Files/ is actually on a different hard drive. The only thing I actually add to my boot drive are iTunes music, changes and modifications to my preferences files and the odd thing I have on my desktop before I have filed it away somewhere.

When I do a media project (which usually involves Final Cut Pro and Photoshop), the Photoshop files go to a disk that I use for pictures and my video and audio go to my media drives. When I am done with the project, if there is anything I really have to keep, it gets backed up onto a DVD (usually video or cool effects I create) or a CD (usually photos, mattes, masks and so on created in Photoshop). Some photos I keep live on the hard disk I use for Photoshop. No video or effects are left on my media drives, which are wiped after every project is finished and paid for (the paid for part is usually an indication that there will be no more changes).

Partly what I am doing is what Symantec tries to do: Keep like with like and make sure things are organized. I would hate to think of what their utility would do with one of my media drives, which are supposed to take in the video in a fragmented state (each video clip is its own file and audio is its own file) and play back a video stream real-time from a collection of widely-scattered fragments (when you consider that the effects, layers and rendered elements are often on a different drive than the main media, these drives are really working hard to do this). Symantec's utility makes a series of assumptions about what should follow what. You cannot know what will follow what until your project is done and layed back to tape or burned onto a DVD (in my case, both). So I imagine they would find a lot of their assumptions to be wrong.

But this is why the hard disk manufacturers came up with drives that are capable of delivering media. A 7200 RPM drive array with large caches will do it for standard video and audio. A 10K array with large caches will work for high definition video and you want to put that into a closet so that your client doesn't have to listen to it whine.

I assert that if your boot drive is capable of delivering standard video, Symantec's utility will not improve the speed of your computer, which is more bound by the speed of the hard disk controller and RAM subsystem than whether or not the files are nicely organized on your hard disk.

I don't put important data on my boot drive. I have my boot drive regularly backed up onto a removable drive that can also boot, through the use of Mike Bombich's Carbon Copy Cloner. I back up my data drives onto glass (CD and DVD). My media drives get wiped. In this situation, there is no need to optimize, as I have all ready optimized workflow.

Symantec's claim was that your applications will load faster because they were all in one place. They also claimed that your computer would boot faster because all of the stuff that it needed to boot was in order, neatly organized for consecutive reads. They were a little less concerned about the creation of new data files because data files always get fragmented as you add to them. I believe that Symantec did optimize the data files but, as one does not always read data consecutively, that was less important to speed and more important to disk recovery in the case of a crash.

I defy anyone who has a hard disk with a large cache and a modern head-actuator mechanism to show me empirical evidence that "optimization" is significantly faster than what I'm doing now.

24th February 2004, 09:50 AM
What you say is correct, and I do more or less the same thing. A more effective way of maintaining file organisation for speed is to have a separate partition or HD for very large files.

However, I have come across computers (not recently) that were extremely fragmented, taking up to 10 minutes to boot, which I reduced down to a minute by defragmenting them. This could occur under OS9 and below, but are less likely under OSX, as it maintains files on the hard drive in a better way.

In OS9, you'd have maybe a few thousand files on a hard disk. Each program was one large file, which was likely to fragment if it were installed while there were many small free spaces on the drive.

In OSX, you have something like 200,000 file entries by default after you've installed the OS. It comes up as about 100,000 if all packages are listed as single files (when really they are multiple files). As 99% of all these files are quite tiny, and as Mac OS X auto-defragments files under 20k in size, it's generally unnecessary to worry about file fragmentation. However, if all your files, including very large ones, are on the same drive/partition, the very large files are very likely to be quite fragmented, and may load much slower than they would if they were stored on the disk in just one or two fragments.

25th February 2004, 03:05 PM
Originally posted by Currawong@Feb 24 2004, 09:50 AM
if all your files, including very large ones, are on the same drive/partition, the very large files are very likely to be quite fragmented, and may load much slower than they would if they were stored on the disk in just one or two fragments.
I should have prefaced my comments to mean that I am discussing OS X exclusively with respect to file defragmentation and the "benefits" of applications such as "Speed Disk." I really have to say that System 9 and below tends to not create a good organizational model for disk drives.

But to answer your comment, the very large files, in actuality, do not exhibit that behavior and that is due to the fact that hard disks today are a whole lot faster. Most apple-supplied drives prior to OS X had a platter speed below 6,000 RPM and head actuator mechanisms that were slower than those today. Presently, Apple uses those slow drives only in laptops and uses them in laptops in order to save battery life.

Data is packed considerably more densly on the new drives than on the old. This is not due to an increase in the number of platters; rather it is due to the increased sensitivity of the read head as well as improvements in the technology of hard disks that make them more reliable and able to record bits of data in a smaller and smaller area using less and less energy to do that.

Because of those factors, the read/write head of these new hard disks have less mass. And, due to advancements in drive technology, the actuator motor is more accurate. the number of times a platter needs to rotate for the head to pick up the requested data has dropped considerably and continues to drop each month as new media comes out.

Thus, if data is scattered on the disk, the time dependencies lie more in the bus that transfers the data from disk to memory than in actual seek times and read times. While a sequential read is almost always faster because the head actuator does not have to move much, the platter is spinning so fast that sequential data reads and non-sequential data reads are read so fast that the read must be buffered in the drive mechanism itself before it is transferred to the computer's memory.

Hence, if you purchase a 7200 RPM drive with an 8M data cache, your computer is mostly reading from that cache on a standard ATA 133 card while the drive stuffs the cache.

If you are working with really large data sets, like video while you are video editing, you will read directly off the drive because you need more than 8M chunks. But the process of video editing is all about non-sequential reads, with audio in a different place than video, which is why for high definition and full-resolution video you are required to use an array.

So I would argue that these disk defragmentation programs are of little use under OS X, as it does defragment small files that will tend to underrun the disk buffer. My drive(s) are plenty fast for everything I am doing without it. I journaled my boot drive under OS X 10.2 and tested its speed. It is a 100G drive with an 8M data cache. With journaling off, I did a series of disk tests that showed my drive to be very fast, indeed. After journaling was turned on, I did the same series of tests. At no time was either a read from or a write to my drive slower due to journaling. boot times are exactly the same as well.

That means I'm not really seeing my disk read -- it's so fast that my computer's subsystems become the slow part. Defragmentation tools assume that you are slowed down by the head actuator moving. If a journaled drive versus an unjournaled drive shows no difference, how would Speed Disk change anything?

Furthermore, I am familiar with how dangerous it is to use Symantec's Norton Utilities on an OS X system. In using Speed Disk, I am taking a horrid chance that I will really mess up my system and really muck up my permissions, as it runs under System 9.x and is no respector of Unix's filing system (even on an HFS+ drive).

Thus I cannot recommend any defragmentation software where one is using OS X. They would undoubtedly do more harm than good, and scarce little good at that.

25th February 2004, 06:57 PM
That's a very interesting explanation. Thanks.

I've used Systemworks 3 to defragment drives in OSX with no problems. I am wary of it. The important data was backed up onto two different media. I do know it's done damage in the past when people started using it on OSX before it had been upgraded to work with file permissions.

26th February 2004, 12:57 AM
One additional comment is that I do not use hard disks that are over 3 years of age. Published specifications on hard drives state Mean Time Before Failure (MTBF) stats that suggest that, after three years you can't count on your drive.

I do not upgrade my computer that often, though if I had a pee cee I would have to in order to use current software, just my hard disks. Thus, I tend to have fairly new, really fast disks.

If I was still using a Centris or a Deforma, I'd probably still be in System 7 or 8 and would be able to use Speed Disk to organize my drive because it wouldn't destroy my permissions. But I'd probably test and see if the new drives I had in my computers actually did improve their performance after spending the time optimizing them. And once I saw no difference, I'd not waste the time.

I have been using video drive arrays for about eight years now. I know how the Avid (and now Final Cut Pro) uses the drives for video delivery to your monitor and to your final output and those drives are really working hard (good to not wait three years to replace media drives). As read back to output a final production, the video and audio are totally non-sequential, yet it is possible to output the full resolution of the video with nary an artifact. That should tell you something about how well drives have improved.

26th February 2004, 08:20 AM
i wouldn't defragment my drive but i would get a copy of Disk Warrior if i generally a paranoid person...

The best way to go is assume your drive is going to die soon and back up accordingly.