[CentOS] Centos/Linux Disk Caching, might be OT in some ways

> Sorry to be the bearer of bad news, but on top of LVM on CentOS/RHEL
> the best assurance your going to get is fsync(), meaning the data is
> out of the kernel, but probably still on disk write cache. Make sure
> you have a good UPS setup, so the disks can flush after main power loss.

Or turn off write caching...