RAID or multiple cache_dir s?

I was about to purchase a new box for squid (my old 2Gb, P90 has served me
well for a year running squid 1.somthing). I spec-ed out a Dell 2300
with 512Mb, 6x9Gb + RAID-0 (Dell PERC-RAID is really AMI MegaRaid which is
supported in 2.0.36 linux kernels (and Redhat 5.2)).

So tonight I was reading up a little on Squid 2.1 (as you would) and note that
you can specify multiple cache_dir lines to run several drives, so I have the
following questions:

 o For a reasonably well used cache, is using multiple cache_dir entries and
   efficient as a hardare RAID-0 box? (Yes I know there will be some
   small performance loss, but will squid make use of all the disks
   efficiently?)

 o Another thread asked the question if a disk (and thus a cache_dir) went
   bad would squid continue to perform well using the remaining disks ?
   Is this true?

 o Whats the maximum limits on Squid? Should I continue to throw disk at a
   box, or buy a separate box. If I can save on RAID, I can afford extra
   memory and so have a 1Gb RAM box - Squid won't break?

 o Is it the general consensus to avoid Transparent proxying if possible, and
   that it is better to force the user to knowingly use the proxy settings in
   their browser?

Thanks for any advice offered.

Paul.

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