[CentOS] Slow RAID Check/high %iowait during check after updgrade from CentOS 6.5 -> CentOS 7.2

[m.roth at 5-cent.us]

Kelly Lesperance wrote:
> I’ve posted this on the forums at
> https://www.centos.org/forums/viewtopic.php?f=47&t=57926&p=244614#p244614
> - posting to the list in the hopes of getting more eyeballs on it.
>
> We have a cluster of 23 HP DL380p Gen8 hosts running Kafka. Basic specs:
>
> 2x E5-2650
> 128 GB RAM
> 12 x 4 TB 7200 RPM SATA drives connected to an HP H220 HBA
> Dual port 10 GB NIC
>
> The drives are configured as one large RAID-10 volume with mdadm,
> filesystem is XFS. The OS is not installed on the drive - we PXE boot a
> CentOS image we've built with minimal packages installed, and do the OS
> configuration via puppet. Originally, the hosts were running CentOS 6.5,
> with Kafka 0.8.1, without issue. We recently upgraded to CentOS 7.2 and
> Kafka 0.9, and that's when the trouble started.
<SNIP>
Really stupid question: are the drives in that the ones that came with the
unit?

      mark, who, a few years ago, found serious issues with green drives in a
                  server....