[CentOS] Software RAID complete drives or individual partitions

Tue Mar 5 13:58:36 UTC 2013
SilverTip257 <silvertip257 at gmail.com>

On Mon, Mar 4, 2013 at 10:53 PM, Chris Weisiger <cweisiger at bellsouth.net>wrote:

> I have been reading about software raid. I configured my first software
> raid system about a month ago.
>
> I have 4 500 Gig drives configured in RAID 5 configuration with a total of
> 1.5TB.
>
> Currently I configured the complete individual drivers as software raid,
> then created a /dev/md0 with the drives
>
>
I've read (and would agree) that using the entire drive can hide the fact
that a softraid is there.  If you set up a partition on the disk and mark
the file system as type "fd" then no matter what you know that disk is part
of a softraid array.

What you configured works.  Is it wrong?  No.


> I then created a /file_storage partition on /dev/md0.
>
> I created my /boot / and swap partitions on a non raid drive in my system.
>
> Is the the proper way to configure software raid?


I generally use LVM on my systems, so my layouts has /boot carved out as
its own partition and then another partition for the LVM PV.  And if you
use standard partitions instead of LVM, then create individual softraid
arrays for each partition.
* Remember, /boot can only be on a raid1 software array.


Veering slightly from your original question...
I recently set up softraid arrays by hand before invoking the Anaconda
installer (on a 6.3 install).  Recent mdadm packages that ship with CentOS
support metadata 1.1 and 1.2 (... actually defaulting to 1.2 I believe),
but GRUB 0.97 only supports metadata 1.0 and not the metadata version that
mdadm defaulted to.  On my CentOS 5 installs in the past I've specifically
set --metadata=0.90 to avert any catastrophes like this.

Fun problem to troubleshoot ... I knew it once that system wouldn't boot
though.  Kind of odd that the installer didn't pick up on the metadata
version and flag it or modify it.  In the end I ended up rescuing the
system by backing up and recreating the /boot softraid with metadata 1.0  :)


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-- 
---~~.~~---
Mike
//  SilverTip257  //