The osd needs to know where it thought data was, in particular so it knows what it has. Then it gets the current map so it knows who to talk to so it can catch back up.
Sent from my iPhone On Oct 22, 2016, at 7:12 AM, xxhdx1985126 <xxhdx1985...@163.com<mailto:xxhdx1985...@163.com>> wrote: Hi, everyone. I'm trying to read the source code that boots an OSD instance, and I find something really overwhelms me. In the OSD::init() method, it read the OSDSuperblock by calling OSD::read_superblock(), and the it tried to get the "current" map : "osdmap = get_map(superblock.current_epoch)". Then OSD uses this osdmap to calculate the acting and up set of each pg. I really don't understand this! Since the OSDSuperblock is read from the disk, the superblock.current_epoch should be an old epoch which is recorded by the last OSD instance that run on this directory. Why use an old "current_epoch" to calculate the acting and up set of each pg? Please help me, thank you:-) ________________________________ [cid:image15424c.JPG@ef7d796d.48843c49]<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. ________________________________ _______________________________________________ ceph-users mailing list ceph-users@lists.ceph.com<mailto:ceph-users@lists.ceph.com> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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