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Prijker · May 19, 2003, 04:41 PM

After fighting during some time with my Mac, i got to a striking conclusion about the performance behaviour of OSX. This is relevant obviously to my system in first place, i'm not sure how this may vary on different systems. Mine is an iMAC DVSE G3 500, 384 Mb RAM, 30 Gb disk, 2 partitions (25 Gb/5 Gb) OSX 10.2.6.

Let's see exactly what i mean.

First, i did some tests with Carbon Copy Cloner (CCC), because i wanted to backup my system. I have 2 partitions (i use the bigger (25 Gb) with OSX and the smaller (5 Gb) with Classic). so i finally did a clone of my system from the bigger to the smaller partition. But, as my idea was to have a cloned system as small as possible in order to later burn it on CDs, i didn't clone the whole system, but only the System and root Library folders (i excluded Applications and Users folders).

So, i got a sort of stripped down version of my system, with no users, no apps, no prefs, and i was thinking what would the system look like when (if) i reboot from the clone... A system similar to those we can find in bootables CDs, that's what i presumed.

So when i rebooted back from the cloned system, i was curious to see how it would be like. To my surprise, but thanks to CCC, everything (except prefs) was exactly like the original system, sames users, same passwords, same privileges! BUT... the performance difference was tremendous. Never saw such a fast OSX system! Couldn't believe it...

At first, i was tempted to conclude that this huge difference in performance was due to my stripped down version of the system: the clone had to rebuild the users file system from scratch, so it only could be faster, i thought.

Trying to verify this possibility, i soon noted that this was wrong. I first did the obvious thing: i cloned back from the 2nd to 1st partition with CCC, and choosed the later as startup disk. But, when i rebooted back from the re-cloned system, performance was not there anymore, only the average speed and behaviour i always have had in OSX...

So, as they were exact clones of one another, there was only now one obvious difference between the 2 systems: the size of the partition they were installed in.

(Of course, there's no place for the usual alternative explanations here: my 2 partitions are defragmented and their directory has been rebuilt with diskwarrior on a regular basis.)

So, AFAIK, my 2 systems are exact clones of one another, thanks to CCC, but the clone on my smaller partition is about 80% faster. Some benchmarks i did:
-partition 1 (big): startup 2'05'', PS7 40', Classic 37'
-partition 2 (small): startup 50' (!), PS7 24' Classic 22'

I can't explain these differences. I've always heard X needs lots of disk space, using continous disk space to swap memory to files, and that's the reason why i had it installed on a 25 Gb partition in the first place. So why do i have now a speed-boosted OSX system, running from a 5 Gb partition? Shouldn't it be the other way?

May be something happened with this clone operation. Don't know what, and don't know if this story is clone-related of partition-related, but, besides benchmarks, there are 2 concrete symptoms i can report (thanks to MenuMeters): first, the amount of used memory is now much lower than before: i hardly fill my 384 Mb of RAM, and at startup, the system only uses about 120 Mb of RAM (it used to take 180 Mb in my old config). Second, the disk activity is much lower, it seems disk access is not required as much as before. This explains why the whole system is so fast now.

Can anyone confirm this?

Victor J. Prijker
shiket@bigfoot.com

Prijker · May 21, 2003, 08:48 AM

looks like nobody cares.

Vic

Rainy Day · May 21, 2003, 12:06 PM

UNIX is a very disk intensive OS. When i dropped in a faster HD, it felt like i had doubled the speed of my Mac. So if you are correct about there being "less disk activity," then that will indeed make the OS feel faster. Of course there might be the same amount of "disk activity," except it might be occurring faster. That is to say, the same number of disk accesses, but each for a shorter period of time, thus giving the appearance of less disk "activity."

This is not the first time i've heard someone say they've seen a performance boost on a smaller partition. In fact, i believe i saw a thread here less than a month ago on the topic. There might be something to that, or it simply could be a matter of where on the HD your partition resides. Depending on drive architecture, certain partitions may have faster access. Drive spec's are, after all, based on average times.

On the other hand, use of virtual memory will increase disk activity significantly. So the more applications you have open at one time, and the more documents and larger the documents those app's have open, the more memory is needed. If it exceeds your Mac's physical RAM, the more the virtual memory system is used, and the more the disk is used, and the slower the OS becomes.

In any event, there's no need for a really large OS X partition as you can easily distribute files among many volumes, if you like (or want, or need), using symbolic links (man ln). Apple uses them:

   /etc@ -> private/etc
   /mach@ -> /mach.sym
   /tmp@ -> private/tmp
   /var@ -> private/var

Whether or not this might speed things up is another question, however, as it could force the drive head to do more traveling (assuming the volumes are all partitions on a single drive). Multiple physical drives would likely give you a performance advantage in this regard.

tooki · May 21, 2003, 12:26 PM

The outermost parts of a disk platter are faster than the innermost, generally speaking, by a small amount, since each track is longer, so that the heads have less distance to travel.

There's a good chance that your 5GB partition is the outermost 5GB; that could explain it.

tooki

Toyin · May 21, 2003, 01:09 PM

Originally posted by tooki:
The outermost parts of a disk platter are faster than the innermost, generally speaking, by a small amount, since each track is longer, so that the heads have less distance to travel.

There's a good chance that your 5GB partition is the outermost 5GB; that could explain it.

tooki

This would be my guess as well. I bet the 5gb partition is the 1st partition. If it's not please let us know.

Rainy Day · May 21, 2003, 01:09 PM

I knew i had seen a recent post on this topic.

Prijker · May 21, 2003, 02:45 PM

>This would be my guess as well. I bet the 5gb partition is the 1st partition. If it's not please let us know.

How can i tell?

gatorparrots · May 21, 2003, 05:06 PM

Launch /Applications/Utilities/Disk Utility.app. Click on the drive's icon in the leftmost pane. It should expand and show you the partitions. They will be listed in order of creation. To doublecheck, click on the Partition tab. They are listed in order from top to bottom on the graphical diagram.

Prijker · May 22, 2003, 08:17 AM

I used Disk Utility which shows my smaller partition is the SECOND one. The first is the big (25 Gb) partition.
So, what next?

vic

Prijker · May 25, 2003, 04:53 PM

i'm afraid this topic is going to die without any further explanations.

The fact IS: it's like i have a new Mac since this experience. Everyday i'm amazed by the overall feeling of the system. I can't believe i used OSX since 2001 without this speed feeling i now get.

And i now am convinced it's partition-related.

The last test i did was drastic: i first burned a clone of my system (cloned with CCC), and then reformated my HD with Disk Utility, re-partitionned with the same 25Gb/5Gb partitions, reinstalled Jaguar on the big partition, and updated to 10.2.6.

Next i reinstalled the clone from CD to the smaller partition.

Next, when i restarted from each partition, i got exactly the same results as before: the system in the 5Gb partition is much more reactive, even though the other partition has a fresh system.

Is there really nothing unusual with this?

Vic

OpenStep · May 25, 2003, 06:04 PM

fragmentation?

Rainy Day · May 25, 2003, 06:29 PM

fragmentation?

Errrrrt. Wrong Answer:

Originally posted by Prijker:
(Of course, there's no place for the usual alternative explanations here: my 2 partitions are defragmented and their directory has been rebuilt with diskwarrior on a regular basis.)

Toyin · May 25, 2003, 09:53 PM

Start up time makes sense. OSX runs a file system check on startup which is a majority of the time. The 5gb portion is 20% smaller so startup is faster. I saw the same effect when I partitioned my HD even back in the OS9 days.

When applications launch, OSX reads several portions of the system to incorporate graphic elements and services into the application. It's possible that a smaller partition makes app launching faster, because there is less hardrive to look through. I'm not sure that with the speed of newer drives this would be significant between 5 and 25gb partitions. The same assumption could apply to reading, writing preferences, accessing Application Support and drivers and other functions that require the OS to access several components of the OS.

If your willing to, I'd be curious to see the same experiment but partition the drive into 3 partitions 1st-5gb, 2nd-20gb, and 3rd-5gb.

yukon · Jun 1, 2003, 10:48 PM

can you do any benchmarks or tests?

on your first install, try backing up your user files, deleting the user, and replacing as few files back into the user folder (clear prefs, etc). does that speed the old install up?

nforcer · Jun 2, 2003, 11:45 PM

I would also be interested in some benchmarks. XBench is free and listed on the software update site of your choice...