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

Gionatan Danti g.danti at assyoma.it
Tue Dec 10 11:23:14 UTC 2019

On 09/12/19 11:26, Daniel Janzon wrote:
> Exactly. The md driver executes on a single core, but with a bunch of RAID5s
> I can distribute the load over many cores. That's also why I cannot join the
> bunch of RAID5's with a RAID0 (as someone suggested) because then again
> all data is pulled through a single core.

MD RAID0 is extremely fast, using a single core at the striping level 
should pose no problem. Did you actually tried this setup?

Anyway, the suggestion from Guoqing Jiang sound promising. Let me quote him:

> Perhaps set "/sys/block/mdx/md/group_thread_cnt" could help here,
> see below commits:
> commit b721420e8719131896b009b11edbbd27d9b85e98
> Author: Shaohua Li <shli at kernel.org>
> Date:   Tue Aug 27 17:50:42 2013 +0800
>      raid5: sysfs entry to control worker thread number
> commit 851c30c9badfc6b294c98e887624bff53644ad21
> Author: Shaohua Li <shli at kernel.org>
> Date:   Wed Aug 28 14:30:16 2013 +0800
>      raid5: offload stripe handle to workqueue


Danti Gionatan
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