[CentOS] First Time Setting up RAID

[John Doe]

From: James B. Byrne <byrnejb at harte-lyne.ca>

> We have a cold server with 32Gb RAM and 8 x 3TB SATA drives mounted in hotswap
> cells.  The intended purpose of this system is as an ERP application and DBMS
> host.  The ERP application will likely eventually have web access but at the
> moment only dedicated client applications can connect to it.
> 
> I am researching how to best set this system up for use as a production host
> employing RAID.  I have read the (minimal) documentation respecting RAID on
> the RedHat site and have found and read a few online guides.  Naturally, in my
> ignorance I have a bunch of questions to ask and I probably have a bunch more
> that I should but do not know enough yet to ask.
> 
>> From what I have read it appears that the system disk must use RAID 1 if it
> uses RAID at all.  Is this the case?  If so, is there any benefit to be had by
> taking two of the 8 drives (6Tb) solely to hold the OS and boot partition? 
> Should these two drives be pulled and replaced with two smaller ones or should
> we bother with RAID for the boot disk at all?
> 
> Given that one or two drive bays will be given over to the OS what should be
> the configuration of the remaining six?  It appears from what I have read that
> RAID 5 is the only viable option.  It also appears that the amount of storage
> available on a RAID5 array with N members is N-1/N. I also read that as the
> number of members increase both latency and the risk of data loss increases. 
> As the amount of disk space we have in this unit (24Tb) is greater than the
> total storage of all our existing hosts it appears that a RAID5 array of 5
> units would leave at least one hot spare in the chassis and two if the OS is
> put on one disk.
> 
> Alternatively, the thought comes to mind that we could do a RAID1 with two
> RAID5 arrays each of which have 3 drives.  Whether one would actually want to
> do that seems to me a bit questionable but it seems to be at least possible.

For some storage servers, we put used the following cards with 2 small drives for the system:
  http://www.sybausa.com/productInfo.php?iid=1134

But do you really need 10+ TB for your ERP+DBM?
I'd just go with a RAID10 for DBs...

JD