JBOD vs arrays vs fibre channel

[Kimery David]

We're trying to decide what kind of disk
configuration to buy for our N4000 database
server. We want 180gb mirrored and we're
mainly concerned with speed. We can't decide
if its better to:
1) go JBOD using 5 sc10 enclosures partially
filled with 40x9gb drives and LVM mirror them.
(we would have 5 dual port scsi interfaces)
(also we would have 20 spindles to spread
out our oracle datafiles, very beneficial with
oracle)
2) go JBOD using 2 fc10 enclosures filled with
20x18gb drives and LVM mirror them.
(its about the same price as #1, allows us to
use fibre channel i/o paths, but not as many
i/o paths and it would give us fewer spindles)
3) buy an fc60 array set up with RAID 1 or 0/1
using sc10 enclosures filled with 40x9gb
drives. It's a little bit more expensive and we've
been told 3-10% slower than JBOD (but a lot
faster than model 20 arrays). But I guess I'm
wondering if the tests that say it's slower are
based on RAID 5 instead of RAID 1 or 0/1. The
reason I question it is because I was recently
told in an HP class that hardware mirroring
(fc60) is supposed to be faster than software
mirroring (LVM).

Can somebody help me please?

[Dave Wherry_1]

I can't give you any definitive answers. I'll just share some my experiences.
We were running SAP on Oracle on a K570 with 2 FC30 arrays, each about half
populated, raid-5. Using 2 Fibre Channel interfaces. The database was about
100GB with around 50 active concurrent users. It was dog slow.
We moved to an XP256 and saw huge performance gains. Then we moved to a V2500
and things are running great.
So, the FC30 arrays on Fibre Channel could not keep up. Raid-5 is typically
slow on writes. The FC30's only have 96MB of cache. The XP has 4GB of cache
so the writes are committed instantly.
I would suggest you look at a solution using Fibre Channel for the speed. Then
connect to some type of array where you can take advantage of large amounts of
cache. The XP is great, but, if your database is not expected to grow much
beyond that, it is an expensive solution. If you have other hosts you can
consolidate onto the XP it may be justified. For one host and one database I
think it's pricey.
EMC has a smaller entry level Symmetrix unit. However it is not as upgradable
as an XP and their prices are usually high also.
If this database is not hit that heavily the FC arrays would probably work
well. As I said, we had 50 heavy hitting users that killed them. If the
database is hit heavily, get an array with lots of cache, more than the FC
arrays hold.