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[2a0a:1580:2000::3f]) by smtp.gmail.com with ESMTPSA id 32sm16170638wrs.5.2021.06.06.23.57.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 06 Jun 2021 23:57:51 -0700 (PDT) Message-ID: <1536e582aba69f723b2a306d9c4176da502f5588.camel@odiso.com> From: aderumier@odiso.com To: Dominik Csapak , Proxmox VE development discussion , pve-devel Date: Mon, 07 Jun 2021 08:57:49 +0200 In-Reply-To: References: <2422013ee08dd4e3abb04ba5360a084beddf5183.camel@odiso.com> User-Agent: Evolution 3.40.2 MIME-Version: 1.0 X-SPAM-LEVEL: Spam detection results: 0 AWL 0.891 Adjusted score from AWL reputation of From: address BAYES_00 -1.9 Bayes spam probability is 0 to 1% DKIM_SIGNED 0.1 Message has a DKIM or DK signature, not necessarily valid DKIM_VALID -0.1 Message has at least one valid DKIM or DK signature HTML_MESSAGE 0.001 HTML included in message RCVD_IN_DNSWL_NONE -0.0001 Sender listed at https://www.dnswl.org/, no trust SPF_HELO_NONE 0.001 SPF: HELO does not publish an SPF Record SPF_PASS -0.001 SPF: sender matches SPF record Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit X-Content-Filtered-By: Mailman/MimeDel 2.1.29 Subject: Re: [pve-devel] ceph create pool with min_size=1 not possible anymore with last gui wizard X-BeenThere: pve-devel@lists.proxmox.com X-Mailman-Version: 2.1.29 Precedence: list List-Id: Proxmox VE development discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 07 Jun 2021 06:58:01 -0000 Le vendredi 04 juin 2021 à 15:23 +0200, Dominik Csapak a écrit : > On 6/4/21 04:47, aderumier@odiso.com wrote: > > Hi, > > > > > Hi, > > > I was doing a training week with students, > > > > and I see that the new ceph wizard to create pool don't allow to > > set > > min_size=1 anymore. > > > > It's currently displaying a warning "min_size <= size/2 can lead to > > data loss, incomplete PGs or unfound objects", > > > > that's ok  ,  but It's also blocking the validation button. > > > > yes, in our experience, setting min_size to 1 is always a bad idea > and most likely not what you want > > what is possible though is to either create the pool on the cli, > or changing the min_size after creation to 1 (this is not blocked) > yes, Sute. I could be great to be able to change size/min_size from the gui too. > > > > > > Some users with small cluster/budgets want to do only size=2, > > > > so with min_size=2, the cluster will go read only in case of any > > osd > > down. > > > > It could be great to allow at least min_size=1 when size=2 is used. > > > > "great" but very dangerous > > > > > also, > > Other setup like size=4, min_size=2, also display the warning, but > > allow to validate the form. > > > > I'm not sure this warning is correct in this case , as since > > octopus, > > min_size > > is auto compute when pool is created, and a simple > > > > ceph osd pool create mypool 128 --size=4  , create a pool with > > min_size=2 by default. > > > > > > the rationale behind this decision was (i think) because > if you have exactly 50% min_size of size (e.g. 4/2) > you can get inconsistent pgs, with no quorum as to > which pg is correct? > (though don't quote me on that) > > so i think its always better to have > 50% min_size of size > Well, afaik, they are no "quorum" on pg consistency for repair currently. if a pg is corrupt, ceph is simply copy data from a pg copy where checksum is ok. and if no checksum is available, it take a random copy. (maybe it need a manual pg_repair in this case). But They are not something like "theses 2 copies have the more majority (quorum) of checksum. (Maybe I'm wrong, but 1 or 2 year ago, Sage have confirmed this on the ceph mailing)