What is "Best Practise" for setting up RAID on a (4) Disk system on MCS 7845 H2 servers?
It is possible, yes; but only as a quick reversion option (i.e. make sure you have the original system backed up using BARS in case a problem occurs).
When you rebuild the server with a new CM version, the RAID array config will probably be wiped and rebuilt, and firmware versions will be changed etc, so you may have problems reverting even if you do this carefully (i.e. shut down the server before splitting, maintaining the correct positions of the disks, etc). You also need to have the server fully populated when doing the build of CM7 or it will see an incorrect disk count and either assume you have a lower spec server or refuse to build.
Typically you would have 2 X RAID1 arrays.
Two logical drives presented to the OS, each one based on two physical disks in a mirrored config.
In general it's not something you need to worry about; most applications have a scripted platform build process that identifies the hardware and builds RAID configs appropriately.
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