[linux-lvm] Best way to run LVM over multiple SW RAIDs?

Roberto Fastec roberto.fastec at gmail.com
Sat Dec 7 17:37:45 UTC 2019

Did you thought about RAID 50 ?

  Messaggio originale  

Da: matorola at gmail.com
Inviato: 7 dicembre 2019 17:17
A: linux-lvm at redhat.com
Rispondi a: linux-lvm at redhat.com
Oggetto: Re: [linux-lvm] Best way to run LVM over multiple SW RAIDs?

On Tue, Oct 29, 2019 at 12:14 PM Daniel Janzon
<daniel.janzon at edgeware.tv> wrote:
> Hello,
> I have a server with very high load using four NVMe SSDs and therefore no HW RAID. Instead I used SW RAID with the mdadm tool. Using one RAID5 volume does not work well since the driver can only utilize one CPU core which spikes at 100% and harms performance. Therefore I created 8 partitions on each disk, and 8 RAID5s across the four disks.
> Now I want to bring them together with LVM. If I do not use a striped volume I get high performance (in expected magnitude according to disk specs). But when I use a striped volume, performance drops to a magnitude below. The reason I am looking for a striped setup is to ensure that data is spread well over the drive to guarantee a good worst-case performance. With linear allocation rather than striped, if load is directed to files on the first PV (a SW RAID) the system is again exposed to the 1-core limitation.
> I tried "--stripes 8 --stripesize 512", and would appreciate any ideas of other things to try. I guess the performance hit can be in the file system as well. I tried XFS and EXT4 with default settings.


a bit more about your system? Like kernel version, io scheduler, etc..
Have you tried with recent kernels MQ (multi-queue) schedulers (noop,
deadline) ?

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