[ceph-users] Erasure coded pools and ceph failure domain setup

Ravi Patel ravi at kheironmed.com
Fri Mar 1 08:02:07 PST 2019


Hello,

My question is how crush distributes chunks throughout the cluster with
erasure coded pools. Currently, we have 4 OSD nodes with 36 drives(OSD
daemons) per node. If we use ceph_failire_domaon=host, then we are
necessarily limited to k=3,m=1, or k=2,m=2. We would like to explore k>3,
m>2 modes of coding but are unsure how the crush rule set will distribute
the chunks if we set the crush_failure_domain to OSD

Ideally, we would like CRUSH to distribute the chunks hierarchically so to
spread them evenly across the nodes. For example, all chunks are on a
single node.

Are chunks evenly spread by default? If not, how might we go about
configuring them?

Cheers,
Ravi

---

Ravi Patel, PhD
Machine Learning Systems Lead
Email: ravi at kheironmed.com



On Thu, 28 Feb 2019 at 14:26, Ravi Patel <ravi at kheironmed.com> wrote:

> Hello,
>
> My question is how crush distributes chunks throughout the cluster with
> erasure coded pools. Currently, we have 4 OSD nodes with 36 drives(OSD
> daemons) per node. If we use ceph_failire_domaon=host, then we are
> necessarily limited to k=3,m=1, or k=2,m=2. We would like to explore k>3,
> m>2 modes of coding but are unsure how the crush rule set will distribute
> the chunks if we set the crush_failure_domain to OSD
>
> Ideally, we would like CRUSH to distribute the chunks hierarchically so to
> spread them evenly across the nodes. For example, all chunks are on a
> single node.
>
> Are chunks evenly spread by default? If not, how might we go about
> configuring them?
>
> Cheers,
> Ravi
>
> ---
>
> Ravi Patel, PhD
> Machine Learning Systems Lead
> Email: ravi at kheironmed.com
>
>

-- 










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