Given a RAID 6 created from 6 drives /dev/md0
which should be used fully for data (no booting from it, root and swap are on a different drive), should I create one partition on that device and then create a file system in that partition, or should I just create a file system on the device?
parted /dev/md0
<create a partion>
mkfs -t ext3 /dev/md0p1
or just
mkfs -t ext3 /dev/md0
And why?
(This is Ubuntu Server, just in case it matters.)
Arguments against the partitioning:
Partitions are strict, obsolete things in the today. A repartitioning mostly a problematic thing. You won't be able to change things in the future.
Raid devices are directly partitionable only in newer kernels.
Thus I suggest you to simply use the whole disk directly, if you won't use some advanced solution. On Linux, LVM is a such advanced "partitioning" system. It enables for you to dynamically create/move/resize/remove partitions, even below a running system, transparently.
There is no added value of creating a partition table there, unless you want to subdivide the amount of space further.
If you need to subdivide the space further you would possibly benefit most from using the logical volume manager instead of creating partitions and then you can still skip the creation of a partition table and address the whole RAID 6 volume as a LVM physical volume.
The advantage of not creating a partition table and not using partitions comes mainly in play when you extend the RAID array with additional disks.