Solid State Drives on a Mac

Question

I am thinking of getting a Solid State drive for the OS only.
Problems that may a Solid State drive may have with the OS.
1) Defrag I never thought that Leopard needed to or did Defrag the Drive but a Sales rep for apple at Best buy said he thought that they did once the mac was shut down. This was done he said to make defraging easier were unlike windows you had to tell it to or schedule a time to do it and leave it on.
From what I read you are not suppose to Defrag Solid state drives.
If this is true is ether a way to disable it in the OS and if so is their a way to tell it what drives to not defrag?
2. I also see programs for sale for the Leopard OS that parts of programs that are left over from installs and when you delete something if this is true this is also not good because it will slowly fill up the drive.
3. If any of the issues above are true I hope the is a work around for it or a update to it to correct this. Hard drives have been the bottle Neck for any OS for a long time and these solid State drives even though new tech seem to be the answer for this.

Answer 1

Network 23,
Well, "never" may have been too strong, but I stand by my statement. OS X just doesn't "defragment" in the commonly accepted sense of the word.
First, it uses "delayed allocation" to reduce the amount- in many cases to zero- of fragmentation that ever occurs.
Second, it does use "adaptive hot-file clustering," whereby an elite class of the most frequently accessed files are written to the drive's "hot band." The limitation on size is <= 10 MBs (if I am not mistaken), and this does occur dynamically. Since this necessarily eliminate any fragmentation for these files, one could state that dynamic fragmentation is occurring. The amount of data we're talking about here is very small, however, so to classify this as generic "defagmentation" would be a stretch.
Third, there is one very limited case when a file will actually be rewritten. Several conditions must be met, the most important being that the file in question must have an allocation of over 8 extents. Since this still applies only to files <= 20 MBs, and given the other fragmentation-prevention measures in place, the conditions under which this occurs will be very, very rare. I will grant, however, that in the rare case that these conditions are all met, the file is indeed relocated to an unfagmented allocation when/if it is opened. Yes, this is dynamic defragmentation.
All this said, "defragmentation" is generally considered to be when a volume is scanned for fragmented file, and those files are all relocated to elimate all fragmentation. This does not occur in OS X.
Scott