Apple Logic Pro /LogicExpress Discussion

GAmoore@... <GAmoore@...> wrote:
: Here is an interesting tidbit. If you have a X-boot only machine (ie. G5), 
: this tech support guy says that you can boot off of another computer (eg. an 
: ibook g4 which is dual boot) into 9, and run 9 utilities - in particular 
: PlusOptimizer to defrag the harddisk.

This sounds pretty dangerous to me. There are a lot of special things in
the OS X filesystem that OS 9 doesn't know or care about, so it's
important that whatever OS 9 utility you use for this handles them safely.
Defragmenting probably doesn't have that much potential for destruction,
but I'd be curious to know if this might screw up drives with journaling
enabled.

-- 
 agreenbu @ nyx . net                             andrew michael greenburg

> This sounds pretty dangerous to me.

I concur. I wouldn't try it myself.

Kamm

GAmoore@... wrote:
> 
> I wish Apple would clear this matter up. We have heard of the ills of 
> fragmented files for years - and it would cut down track counts and such 
> in digital audio.

Heres how I defrag my audio drive. I backup my entire Lacie 160GB fw 
drive to my internal 160gb backup drive. Erase it, then copy everything 
back. Bam its defragged as best as its gonna get. And FYI, it has not 
helped a single bit in getting any higher track counts or less of a CPU 
load. Hate to say it but its not really worth it to even bother..

-- 
Chris

http://www.descentrecords.com

> Heres how I defrag my audio drive. I backup my entire Lacie 
> 160GB fw drive to my internal 160gb backup drive. Erase it, 
> then copy everything back. Bam its defragged as best as its 
> gonna get. And FYI, it has not helped a single bit in getting 
> any higher track counts or less of a CPU load. Hate to say it 
> but its not really worth it to even bother..

I tend to agree with Chris that defragging isn't likely to make much of a
difference unless the disk is really fragmented badly and you are accessing
a lot of audio simultaneously. Even then, if it is a FireWire connection to
the computer, the FireWire could end up being more of a bottleneck than the
fragmented files. FireWire is 400 Mbps (mega "bits" per second). A Serial
ATA drive is 150 MBps (mega "Bytes" per second). That's equivalent to 1,200
mega bits per second. That's 3x faster than a FireWire 400 interface.

Still, 400 Mbps is damn fast. You can get 50 MB of data every second. That's
an entire CD Wave track in one second. Or eight entire CD tracks in 8
seconds.

If you have 20 mono audio tracks at 44.1kHz and 16 bits, that's 88,200 bytes
per second times 20 = 1.764 MBps. Well within the 50 MBps that's available.

Double check my math. I did the calculations fast and didn't double check.

Kamm

> That message came from Alsoft (the maker of Diskwarrior) 
> which would seem to be fairly authoritarian. Diswarrior 3.02 
> claims to be "X native" and is one of the leading disk 
> utilitties - and it was recommended in a MacWorld article 
> recently along with other maintence programs. 

If you are saying that they have an OS9 product that is OSX aware, then I
take back my concern. I got the impression that it was just a plain OS9
application being used to defrag an OSX disk. I can't see how that could
come even close to working.

Kamm

Chris Coccia <mothra@...> wrote:
: 
: GAmoore@... wrote:
: > 
: > I wish Apple would clear this matter up. We have heard of the ills of 
: > fragmented files for years - and it would cut down track counts and such 
: > in digital audio.
: 
: Heres how I defrag my audio drive. I backup my entire Lacie 160GB fw 
: drive to my internal 160gb backup drive. Erase it, then copy everything 
: back. Bam its defragged as best as its gonna get. And FYI, it has not 
: helped a single bit in getting any higher track counts or less of a CPU 
: load. Hate to say it but its not really worth it to even bother..

Well, as soon as you're playing back more than one audio track at the same
time, the drive has to skip back and forth if the files are defragmented.
Writing the files to the drive interleaved in the same way that they are
used in the song might work, but no defragmenting software would know to
do this, or how.

When you first do a multiple-track audio recording, they probably land on
the drive in a way that is more or less interleaved, and that's probably
about as efficient as you can be with regard to improving track counts via
data arrangement.
Defragmenting files that are written in this manner would actually hurt
performance (theoretically).

-- 
 agreenbu @ nyx . net                             andrew michael greenburg

Kamm Schreiner <kamm@...> wrote:
: 
: > Heres how I defrag my audio drive. I backup my entire Lacie 
: > 160GB fw drive to my internal 160gb backup drive. Erase it, 
: > then copy everything back. Bam its defragged as best as its 
: > gonna get. And FYI, it has not helped a single bit in getting 
: > any higher track counts or less of a CPU load. Hate to say it 
: > but its not really worth it to even bother..
: 
: I tend to agree with Chris that defragging isn't likely to make much of a
: difference unless the disk is really fragmented badly and you are accessing
: a lot of audio simultaneously. Even then, if it is a FireWire connection to
: the computer, the FireWire could end up being more of a bottleneck than the
: fragmented files. FireWire is 400 Mbps (mega "bits" per second). A Serial
: ATA drive is 150 MBps (mega "Bytes" per second). That's equivalent to 1,200
: mega bits per second. That's 3x faster than a FireWire 400 interface.
: 
: Still, 400 Mbps is damn fast. You can get 50 MB of data every second. That's
: an entire CD Wave track in one second. Or eight entire CD tracks in 8
: seconds.
: 
: If you have 20 mono audio tracks at 44.1kHz and 16 bits, that's 88,200 bytes
: per second times 20 = 1.764 MBps. Well within the 50 MBps that's available.
: 
: Double check my math. I did the calculations fast and didn't double check.

Of course, no drive mechanism can deliver sustained throughput that even
approaches the speed of the bus being used. A typical modern 7200RPM SATA
drive, while capable of bursting to 150MB/s while reading cached data, will
probably deliver a sustained throughput of around 40MB/s at best. Of
course, the more devices you have on a Firewire bus or an SATA bus, the
more the bandwidth needs to be shared, and you will max out if those
devices are all moving data simultaneously.

-- 
 agreenbu @ nyx . net                             andrew michael greenburg

> Of course, no drive mechanism can deliver sustained 
> throughput that even approaches the speed of the bus being 
> used. A typical modern 7200RPM SATA drive, while capable of 
> bursting to 150MB/s while reading cached data, will probably 
> deliver a sustained throughput of around 40MB/s at best.

Good point. I just took a quick look and found some that had sustained rates
of up to 70 MBps, but it apparently varies a lot according to drive and
manufacturer.

Kamm

> Regarding sustained rates : Wouldn't you get more throughput 
> if you had two drives hooked to firewire - so that the delays 
> in head repositioning on one drive allow the bandwidth for the other.

Yes, but does Logic let you spread your audio files out among several
drives? That's a serious question. I don't know the answer.

> Regarding defragging : I think I am in the situation now 
> where i have various gigs free but there might only be 50mb 
> free space chunks. So what happens when I go to record 6 
> minutes of stereo audio that takes up 60 mb? Couldn't that 
> cause a click or glitch at the point it needs to stop 
> fragment the incoming file? 

I doubt it would cause any problem because your hard drive has a pretty
large buffer and the data is coming in pretty slow as far as the hard drive
is concerned. I don't think it would be a big deal. On top of that, I
suspect Logic is buffering that audio in RAM too. If the disk gets stuck
doing something for a second or two, Logic will just use up more RAM. At
least that's what I think would happen.

And yet on top of that, UNIX also has write behind buffering of data, so
that even if Logic isn't buffering, the OS certainly could be. It is
possible that Logic forces the OS to commit the data right away, but I don't
know enough about UNIX or OS X to talk intelligently about that. I do have a
high confidence level that the Logic guys anticipate that kind of thing and
that it shouldn't be an issue.

Kamm

GAmoore@... <GAmoore@...> wrote:
: Regarding sustained rates : Wouldn't you get more throughput if you had two 
: drives hooked to firewire - so that the delays in head repositioning on one 
: drive allow the bandwidth for the other.

Well, the drives won't coordinate their efforts exactly, but sure. The bottom
line is that you won't get more total throughput than the bus allows, so
the bus will eventually become a bottleneck as you add more devices do it.

If I have two drives that are capable of putting out 30 MB/s each, and I
read from both of them simultaneously at the same priority across 400Mb
Firewire, the throughput on each will be capped at somewhere below 25 MB/s
average (allowing for protocol overhead). My total throughput will be
greater than that of either drive individually, though. You could build a
RAID-0 array out of external firewire drives and probably get pretty close
to pushing the max throughput of the bus.

: Regarding defragging : I think I am in the situation now where i have various 
: gigs free but there might only be 50mb free space chunks. So what happens 
: when I go to record 6 minutes of stereo audio that takes up 60 mb? Couldn't that 
: cause a click or glitch at the point it needs to stop fragment the incoming 
: file?

Stereo audio requires so little speed that it can be fragmented all over
the place with no glitches. Now, once you start accessing multiple files
simultaneously that are fragmented randomly all over the drive, it may
start to have an effect on performance.

-- 
 agreenbu @ nyx . net                             andrew michael greenburg

Kamm Schreiner <kamm@...> wrote:
: 
: > Regarding sustained rates : Wouldn't you get more throughput 
: > if you had two drives hooked to firewire - so that the delays 
: > in head repositioning on one drive allow the bandwidth for the other.
: 
: Yes, but does Logic let you spread your audio files out among several
: drives? That's a serious question. I don't know the answer.

I'm pretty sure that you can only set a single recording path, but you can
import files into a project from any location once they already exist.

Creating a software RAID in Disk Utility is probably the simplest way to
achieve the desired effect for recording.

-- 
 agreenbu @ nyx . net                             andrew michael greenburg