I'm pretty certain that the write returns as complete only after all active OSDs for a PG have completed the write regardless of min_size.
________________________________ [cid:image87d2ad.JPG@6e2c58b3.4d9df465]<https://storagecraft.com> David Turner | Cloud Operations Engineer | StorageCraft Technology Corporation<https://storagecraft.com> 380 Data Drive Suite 300 | Draper | Utah | 84020 Office: 801.871.2760 | Mobile: 385.224.2943 ________________________________ If you are not the intended recipient of this message or received it erroneously, please notify the sender and delete it, together with any attachments, and be advised that any dissemination or copying of this message is prohibited. ________________________________ ________________________________ From: ceph-users [ceph-users-boun...@lists.ceph.com] on behalf of Oliver Humpage [oli...@watershed.co.uk] Sent: Friday, December 09, 2016 2:31 PM To: ceph-us...@ceph.com Subject: Re: [ceph-users] 2x replication: A BIG warning On 7 Dec 2016, at 15:01, Wido den Hollander <w...@42on.com<mailto:w...@42on.com>> wrote: I would always run with min_size = 2 and manually switch to min_size = 1 if the situation really requires it at that moment. Thanks for this thread, it’s been really useful. I might have misunderstood, but does min_size=2 also mean that writes have to wait for at least 2 OSDs to have data written before the write is confirmed? I always assumed this would have a noticeable effect on performance and so left it at 1. Our use case is RBDs being exported as iSCSI for ESXi. OSDs are journalled on enterprise SSDs, servers are linked with 10Gb, and we’re generally getting very acceptable speeds. Any idea as to how upping min_size to 2 might affect things, or should we just try it and see? Oliver.
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