VLDB, RAID, and clustering

Hi,

The workload of a system I am developing/supporting is about to increase
substantially.

The system revolves around one db with many lookup tables built around a >
50Gb table whose workload largely consists of SELECTs againt this, and a
users db tracking each hit against the main Db (doing lots of
SELECT/UPDATE/INSERT statements for each hit).

The users Db is starting to drag system performance. So, to head off a
future crisis, I'm thinking of recomending a clustered SQL solution, with an
extrernal disk array setup as as (a) stripped and mirrored array(s).

Basically, I'm looking for some comment on possible disk configurations
(with another system of comparable size I have had much success with
splitting indexes, lookups, and data tables across physically and logically
distinct drives).

Internal to the clusters, host O/S, program files, and swap files on RAID 1
drives (partioned to have swap files on own sensibly sized logical disks).

External array:-

- TempDb (and misc storage) RAID 1 pair of disks
- Transaction log on RAID 1 pair of disks

I don't really yet have the detailed knowledge to know which of the
following 2 options are best (if indeed they make any difference):-

option a - Host user and main db on logically and physically distinct
RAID 0 + 1 drives

option b - Have 1 big RAID 0 + 1 drive to host both user and main db

(I know the larger the number of drives within a particular array , the
greater the chance of array failure)

I guess the issue lying behind this is:-

If I host main tables, lookup tables, indexes etc. across a stripped and
mirrored array, will the parrallelism this offers render superfluous the idea
of hosting separate databases (which I don't wish to be in contention) or
different components of a database on logically and physically distinct
disks.


Thanks in advance for help, comment, suggestions, and pointers :)


Craig






- N.b. Backups hosted on separate NAS (or at least copied there)











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