>>>>> "Andrew" == Andrew Luke Nesbit <em...@andrewnesbit.org> writes:
Sorry for the delay in replying! Andrew> On 03/04/2019 02:40, John Stoffel wrote: Andrew> [...] >> 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 Andrew> /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 Andrew> Why would you explicitly use MD underneath LVM? I have Andrew> compared the two from a user's level and a best practices Andrew> perspective. My understanding is that LVM uses MD for its low Andrew> level operations anyway. I would explicitly do it for manageability. And separation of the layers. I like the mdadm for my RAID layers, with LVM on top so I can create LVs and them move them around without having to think about it as much. Andrew> What do we gain by using `mdadm --create` instead of using the Andrew> equivalent LVM commands to set up the RAID array? I haven't seen as good a set of tools and reporting of configuration from the lvm tools as I have from the mdadm tools. But... I could be wrong and just a stuck in the mud old fossile. :-) But in this case I think it also brings the benefits of spreading the load across more CPUs, since I *suspect* that LV and it's RAID implementation might be more bottle-necked than the mdadm code is. But it doesn't hurt to test! If this is a new setup, ideally the user would have the time to do some test setups, write his data, and see how the performance is with different setups. You don't need to even run iozone or anything, just a simple 'time /path/to/command args' might be enough to show you which is better. _______________________________________________ linux-lvm mailing list linux-lvm@redhat.com https://www.redhat.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
