[linux-lvm] LVM RAID10 busy 100%

[Andrew Luke Nesbit]

On 03/04/2019 02:40, John Stoffel wrote:

[...]

> I'd probably re-do the RAID using RAID4 (fixed parity disk) since
> you're (probably) just doing a bunch of writing of video files, which
> are large streaming writes, so you won't pay the penalty of the
> Reade/Modify/Write cycle that RAID4/5 has with lots of small files
> being writteing.  But I'd also be using MD under-neath LVM, with XFS on
> top.  Something like this:
>
>   1.   partition each disk with a single whole disk partition
>   2.   mdadm --create /dev/md0 --level=raid4 --raid-devices=8
/dev/sd[a,b,c,e,f,g,k,l]1
>   3.   pvcreate /dev/md0
>   4.   vgcreate data /dev/md0
>   5.   lvcreate -L +12T -n data data
>   6.   mkfs.xfs /dev/mapper/data-data

Why would you explicitly use MD underneath LVM?  I have compared the two
from a user's level and a best practices perspective.  My understanding
is that LVM uses MD for its low level operations anyway.

What do we gain by using `mdadm --create` instead of using the
equivalent LVM commands to set up the RAID array?

Andrew