Lots of good thoughts above: here are my 2 cents:
A LOT depends on the nature of the workload you intend
to give your storage subsystem.
Because the technology is rather mature, particularly
with the widespread availability of perpendicular magnetic
recording and the largest caches e.g. 64 MB per HDD,
a multi-drive RAID effectively multiplies that cache
for RAID-0 arrays: e.g. 4 x HDDs @ 64MB cache = 256 MB cache.
Given current SSD prices, it's hard to beat rotating platters
in terms of cost per gigabyte -AND- in terms of performance
that is acceptable for SOME workloads -- but NOT ALL workloads.
If fail-safe redundancy is ABSOLUTELY NECESSARY, then of course
a RAID-0 is the WRONG WAY.
A LOT also depends on the power of your RAID controller(s):
a hardware RAID controller with a very large on-board cache,
particularly one that uses an x8 lane PCI-E 2.0 interface,
is a must for any serious storage subsystem.
We've been looking at storage technology for a long time,
e.g. ever since super minicomputer days, and it is clear
there is an ever widening performance gap between CPUs and RAM,
on the one hand, and rotating platters, on the other hand.
Rotating disk drives are getting much larger
without getting much faster, in general.
Even THE fastest SAS/6G HDDs at 15,000 rpm cannot approach
the extremely low access times of modern SSDs.
We have decided to wait, and our next purchase will
probably be a SAS/6G controller, like Intel's RS2BL080
or RS2BL040:
http://www.intel.com/Products/Server/RAID-controllers/RS2BL080/RS2BL080-overview.htm
Then, as soon as SATA/6G SSDs become more widely available,
we expect that the prices of SATA/3G SSDs will fall,
giving us more options to choose from, and also
it's more likely that SSD technology will have matured
even more by then.
For example, Intel's Matrix Storage Technology
ICH10R does not (yet) support the TRIM function,
to my knowledge. (Please someone correct me on
this point, if I am in error.)
So, a safe approach, for now, is to invest in a powerful PCI-E
SAS/6G RAID controller and wire it to fast 15,000 rpm
SAS/6G HDDs like Seagate's Savvio 15K.2:
http://www.seagate.com/www/en-us/products/servers/savvio/savvio_15k.2/
SATA/6G SSDs should be plug-compatible, by the
time they do become more widely available.
SATA/3G SSDs are already pushing the 300MB/sec. limit
of the SATA-II interface, so it's reasonable to expect
SATA/6G SSDs to exceed 300MB/second.
We also just installed 2 of these Enhance Tech X14's,
in anticipation of migrating to the 2.5" form factor:
http://www.newegg.com/Product/Product.aspx?Item=N82E16816201054
The X14 is much better built that Athena's comparable SATA backplane
unit, which suffers from a flimsy SATA port connection to the PCB
(breaks loose when a tight SATA connector is pulled out). See
Customer Reviews of the latter here:
http://www.newegg.com/Product/Product.aspx?Item=N82E16816119006
This also happened to us:
"Cons: After one insertion and removal of a SATA cable into one of the SATA sockets a simple removal of the cable has ripped the socket right off the printed circuit board, leaving the socket with solder covered leads dangling at the end of the SATA cable."
So, we recommended the X14 to Newegg, and I'm happy
to say that they agreed with our recommendation,
even though the X14 is much more expensive.
MRFS