[CentOS] LVM hatred, was Re: /boot on a separate partition?

Wed Jun 24 13:14:34 UTC 2015
Chris Adams <linux at cmadams.net>

Once upon a time, Marko Vojinovic <vvmarko at gmail.com> said:
> On Tue, 23 Jun 2015 18:42:13 -0700
> Gordon Messmer <gordon.messmer at gmail.com> wrote:
> > I wondered the same thing, especially in the context of someone who 
> > prefers virtual machines.  LV-backed VMs have *dramatically* better
> > disk performance than file-backed VMs.
> Ok, you made me curious. Just how dramatic can it be? From where I'm
> sitting, a read/write to a disk takes the amount of time it takes, the
> hardware has a certain physical speed, regardless of the presence of
> LVM. What am I missing?

File-backed images have to go through the filesystem layer.  They are
not allocated contiguously, so what appear to be sequential reads inside
the VM can be widely scattered across the underlying disk.

There are plenty of people that have documented the performance
differences, just Google it.

Chris Adams <linux at cmadams.net>