[CentOS] Raid on centos

Fri Feb 7 13:56:51 UTC 2014
James Hogarth <james.hogarth at gmail.com>

On 7 February 2014 11:34, John Doe <jdmls at yahoo.com> wrote:

> From: Jeff Allison <jeff.allison at allygray.2y.net>
> > Ok I've a HP mircoserver that I'm building up.
> > It's got 4 bays for be used for data that I'm considering setup up woth
> > softwere raid (mdadm)
> > I've 2 x 2TB 2 x 2.5 TB and 2 x 1TB, I'm leaning towards usig the
> > 4 2.x TB is a raid 5 array to get 6TB.
> Just a reminder that (at least in the Gen8) bays 1+2 are 6G, but
> bays 3+4 are 3G.  So you might lose a tiny bit of speed if you
> pair them in a RAID5.
> For the "migration", to make it clean and simple, I would just copy the
> data temporarily on USB external disks; which I would use anyway for
> backups.
He said HP Microserver which is a bit different ...

The OP should be aware of alternative BIOSes avaliable for it such as this


This then opens up the possibilities as there is then a full 6 SATAIII 6GB
ports avaliable rather than the original 4 internal, one SATA optical (no
AHCI etc) and one eSATA ...

My N40L for example has 4 data drives in the cages and a 5th drive mounted
where the optical would usually go for a system disk...

I frankly don't care if I lose the system disk - it's quick to rebuild the
system - it's the data I care about.

On this I'm running F20 rather than C6 primarily for the better BTRFS (when
el7 rolls around I'll contemplate a rebuild to that then) and the four data
disks in a BTRFS pool with a raid1 profile ...

The specific benefits of this, in no particular order, and the reason I did
so (non-exhaustive list) are:
1) Daily snapshots at no space 'cost' due to COW
2) Dedup (see bedup) of large files when i need to expose them in multiple
places without resorting to hard links - each file remains independent if I
need to change it.
3) Filesystem level transparent compression of files where it's worthwhile.
4) Trivial to change/add disks to provide additional space when I'm close
to capacity.
5) Regular (2-4 weeks I usually do it) scrubs to catch any bitrot that
might occur.
6) Uneven sized disks still work in RAID1 (I have 2x2Tb and 2x3TB) without
incurring the 'minimum size of disk' penalty.