How does iTunes work?

[jvaska]

Just curious...

Does iTunes read the file straight from the disk while playing it back or does it in some way cache it?

I ask because I wonder if it's a good idea to store 10 gigs of music on the same drive that I backup alot of work to (before it goes to a cd backup)...

?

 

[lopresmb]

yep. from your HD, but that drive can be connectred to your computer anywhere. I have all my music on a second Hard drive, so it doesn't slow up my system drive.

 

[rainman::|:|]

Well it's not good practice at all for an app to read straight from the disk, for a file like this-- it would tie up your read heads the whole time music was playing. What it does is loads the song into RAM and plays it from there. But I'm not sure if it does it one-at-a-time, or loads the next 10 in line, or what. Reading a 3meg file only takes a second or so anyway, so it's not likely to affect CD burning, which is also pre-loaded (buffered) into RAM. I wouldn't worry about it unless you experience problems.

as lopresmb said, you can always have the library on a separate disk if it's a big concern.

 

[Palad1]

Is it possible to create a RAM disk in Tiger?

Just toying around with a stupid idea

 

[Makosuke]

A little time looking at the Activity Monitor sort of indicates how it reads files, which looks to be very different from the iPod's caching scheme. It looks like iTunes does *not* cache the whole file, but rather reads small chunks of data every few seconds while playing. If you scrub around slowly, it reads each chunk of the file as needed, so ends up reading data MUCH faster (1+MB/s) than while playing (little bursts in the dozens of KB/s).

The data rate is so low I seriously doubt it's any kind of issue no matter what you're worried about.

And yes, it is possible to create a RAM Disk in OSX, but it's also basically useless.