[OT] info about filesystem directly on disk device and not partition

[Rick Stevens]

On 03/23/2010 03:55 PM, Gianluca Cecchi wrote:
> Hello,
> sorry for the off-topic.
> Tipically when I work with LVM on Linux (RHEL/CentOS 5 and/or Fedora
> 11/12), I create the physical volume directly on the whole disk.
> Historically one created a partition on the disk, eventually big as the
> whole disk and then marked it as 8e type (LVM), and then the PV on the
> partition.
> With recent kernels/LVM2 user tools it became safe/normal to create it
> directly on disk device, and so I normally do.
>
> What about same thing for ext3 filesystem?
> So creating for example an ext3 filesystem directly on the /dev/sda device?
> Does this imply any risk/problem?
>
> Does it change anything if the underlying device is instead managed by
> device-mapper-multipath, so for example the device name is
> /dev/mapper/mpath1?
>
> I ask because, used with creating PVs, VGs and LVs, today I had to
> create a plain filesystem on mpath device and forgot to create a
> partition on it but issued the mkfs command directly on it... and then
> mounted it... now I have this doubt

I've built filesystems (ext2 and ext3) for a long time on thumb drives
(and certainly on floppies) without partitioning, so yes, you can do it.

On the other hand, a partition table doesn't take any capacity away
from a drive so there's really no need to skip partitioning other than
laziness. :-)  (and yes, I can be a lazy cuss)
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