Do you have seperate Drives for the Transaction Logs and OS?

I would expect READ / Write Delays if you had them on the same
Spindles/drives.

This is why it is not Best practice.

Open perfmon and collect the physical disk - sec/transfer counter for your
DB & Log drives.  I bet they're not within the recommendations of the MS
Whitepaper "Optimizing Storage Performance for Exchange 2003".

Slow disk is the number one cause of preceived performance problems in
Exchange.

I don't understand  what you're talking about when you say " but I would
expect to be given my pink slip if I recommended it as a customer solution
for a Database due to
the lack of redundancy and high risk we would assume."

RAID 1 is 100% redundant, it's mirroring..

The Microsoft Whitepaper "Disk Subsystem Performance Analysis for Windows"
gives a set of criteria where it is appropriate to use RAID 5.
http://download.microsoft.com/download/e/b/a/eba1050f-a31d-436b-9281-92cdfeae4b4
5/subsys_perf.doc#_Toc72126973
Quoting from the paper:

"RAID-5 might be the right choice for a write-heavy workload if the
following is true:

·         The workload consists of large requests in comparison to the array's
stripe unit size (that is, they constitute several complete stripes of data
on average), or the controller has a write-back cache, allowing writes to be
delayed and coalesced into full stripes, and

·         The workload is largely sequential (in terms of LBNs), and

·         The array controller can detect and optimize for full stripe
writes, and

·         The number of spindles is reasonable, as described in "Rules of
Thumb" later in this paper, and

·        Cost is a serious issue"

Exchange databases are a random workload that uses a 4K (small requests) IO
size.  A three drive RAID 5 set uses more spindes at higher cost and
provides lower performance than a mirror.  I don't see where any of the
criteria are met for a RAID 5 recommendation.

The same paper discusses the characteristics of RAID 1/0+1/10:

"    ·         Performance:
       For write requests, both parts of a mirror must be updated, reducing
the available write throughput by >50% for 2-way mirrors, >66% for 3-way
mirrors, and so on. On the other hand, read performance improves         as
the number of mirrors in each set increases.
·         Reliability:
For an M-way mirrored set, all M disks must be lost before data is lost. In
the common case of a simple 2-way mirror, MTBF is now increased because it
is the longer of two semi-independent disk lifetimes. In most cases, the
mirror can be restored quickly (for example, by replacing the disk by hand
or using a hot spare), further reducing the window of vulnerability. For
non-trivial mirrored striped arrays, most multi-disk failures are
survivable.

·         Availability:
If connectivity is lost to one disk, or even M-1 disks of every M-mirrored
set in a striped array, work can still proceed, albeit at a different level
of throughput; failure of a mirror spindle decreases read performance and
increases write performance for that set. When disconnected disks become
reachable again, they can be synchronized back to the corresponding active
disks, thereby restoring the original array characteristics."

Both a RAID 5 set with 3 disks and a Mirror can withstand the failure of a
single drive.  I'm not seeing a redundancy problem that would result in a
pink slip here.  I do see a potential perfrormance problem with RAID 5 that
could however result in that pink slip.

"I am using a calculator developed by Exchange Rangers and have used it
without any issues (both theoretically and in the real world)  It uses the
same calculations as John Fullbright had illustrated with more
considerations."

The "Exchange Rangers", all 68 of them collaborating to produce one
calculator.  The mental image of Adrian, Scott, Lee, Ace, Elias, etc. all in
one room is enough to make you go blind.

Wasn't that Greg D.'s *other little band of merry men, besides the
Blackbelts?

Makes you wonder; what came first, the chicken or the egg?