Begou
Cc:ceph-users@ceph.io
Subject: [ceph-users] Re: EC Profiles & DR
Hi Patrick,
Yes K and M are chunks, but the default crush map is a chunk per host,
which is probably the best way to do it, but I'm no expert. I'm not sure
why you would want to do a crush map with 2 chunks per host and min
On Wed, Dec 6, 2023 at 9:25 AM Patrick Begou
wrote:
>
> My understood was that k and m were for EC chunks not hosts. Of
> course if k and m are hosts the best choice would be k=2 and m=2.
A few others have already replied - as they said if the failure domain
is set to host then it will put
o way around it. I was happy when I got the
extra hosts.
Best regards,
=
Frank Schilder
AIT Risø Campus
Bygning 109, rum S14
From: Curt
Sent: Wednesday, December 6, 2023 3:56 PM
To: Patrick Begou
Cc: ceph-users@ceph.io
Subject: [ceph-user
Hi Patrick,
Yes K and M are chunks, but the default crush map is a chunk per host,
which is probably the best way to do it, but I'm no expert. I'm not sure
why you would want to do a crush map with 2 chunks per host and min size 4
as it' s just asking for trouble at some point, in my opinion.
Le 06/12/2023 à 00:11, Rich Freeman a écrit :
On Tue, Dec 5, 2023 at 6:35 AM Patrick Begou
wrote:
Ok, so I've misunderstood the meaning of failure domain. If there is no
way to request using 2 osd/node and node as failure domain, with 5 nodes
k=3+m=1 is not secure enough and I will have to
You can structure your crush map so that you get multiple EC chunks per
host in a way that you can still survive a host outage outage even though
you have fewer hosts than k+1
For example if you run an EC=4+2 profile on 3 hosts you can structure your
crushmap so that you have 2 chunks per host.
On Tue, Dec 5, 2023 at 6:35 AM Patrick Begou
wrote:
>
> Ok, so I've misunderstood the meaning of failure domain. If there is no
> way to request using 2 osd/node and node as failure domain, with 5 nodes
> k=3+m=1 is not secure enough and I will have to use k=2+m=2, so like a
> raid1 setup. A
Hi Patrick,
If your hardware is new and you are confident in the support of your
hardware and can consider future expansion, you can possibly start with a
k=3 and m=2.
It is true that we generally prefer to divide (k) the data by an exponent
2, but k=3 does the job
Be careful, it is
Ok, so I've misunderstood the meaning of failure domain. If there is no
way to request using 2 osd/node and node as failure domain, with 5 nodes
k=3+m=1 is not secure enough and I will have to use k=2+m=2, so like a
raid1 setup. A little bit better than replication in the point of view
of
Hi,
To return to my comparison with SANs, on a SAN you have spare disks to
repair a failed disk.
On Ceph, you therefore need at least one more host (k+m+1).
If we take into consideration the formalities/delivery times of a new
server, k+m+2 is not luxury (Depending on the growth of your
Hi Matthew,
To make a simplistic comparison, it is generally not recommended to raid 5
with large disks (>1 TB) due to the probability (low but not zero) of
losing another disk during the rebuild.
So imagine losing a host full of disks.
Additionally, min_size=1 means you can no longer maintain
On Tue, Dec 5, 2023 at 5:16 AM Patrick Begou
wrote:
>
> On my side, I'm working on building my first (small) Ceph cluster using
> E.C. and I was thinking about 5 nodes and k=4 m=2. With a failure domain
> on host and several osd by nodes, in my mind this setup may run degraded
> with 3 nodes
Hi Robert,
Le 05/12/2023 à 10:05, Robert Sander a écrit :
On 12/5/23 10:01, duluxoz wrote:
Thanks David, I knew I had something wrong :-)
Just for my own edification: Why is k=2, m=1 not recommended for
production? Considered to "fragile", or something else?
It is the same as a replicated
: Robert Sander
Sent: 05 December 2023 09:20
To: ceph-users@ceph.io
Subject: [ceph-users] Re: EC Profiles & DR
CAUTION: This email originates from outside THG
On 12/5/23 10:06, duluxoz wrote:
> I'm confused - doesn't k4 m2 mean that you can loose any 2 out of the 6
> osds?
Yes
On 12/5/23 10:06, duluxoz wrote:
I'm confused - doesn't k4 m2 mean that you can loose any 2 out of the 6
osds?
Yes, but OSDs are not a good failure zone.
The host is the smallest failure zone that is practicable and safe
against data loss.
Regards
--
Robert Sander
Heinlein Consulting GmbH
-users] Re: EC Profiles & DR
CAUTION: This email originates from outside THG
Thanks David, I knew I had something wrong :-)
Just for my own edification: Why is k=2, m=1 not recommended for
production? Considered to "fragile", or something else?
Cheers
Dulux-Oz
On 05/12/202
On 12/5/23 10:01, duluxoz wrote:
Thanks David, I knew I had something wrong :-)
Just for my own edification: Why is k=2, m=1 not recommended for
production? Considered to "fragile", or something else?
It is the same as a replicated pool with size=2. Only one host can go
down. After that you
And the second issue is with k4 m2 you'll have min_size = 5 which
means if one host is down your PGs become inactive, which is what you
most likely experienced.
Zitat von David Rivera :
First problem here is you are using crush-failure-domain=osd when you
should use
Thanks David, I knew I had something wrong :-)
Just for my own edification: Why is k=2, m=1 not recommended for
production? Considered to "fragile", or something else?
Cheers
Dulux-Oz
On 05/12/2023 19:53, David Rivera wrote:
First problem here is you are using crush-failure-domain=osd when
First problem here is you are using crush-failure-domain=osd when you
should use crush-failure-domain=host. With three hosts, you should use k=2,
m=1; this is not recommended in production environment.
On Mon, Dec 4, 2023, 23:26 duluxoz wrote:
> Hi All,
>
> Looking for some help/explanation
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