On 20/09/2017 10:59, Sam Huracan wrote: > Hi Cephers, > > I've read about new BlueStore and have 2 questions: > > 1. The purpose of BlueStore is eliminating the drawbacks of POSIX when > using FileStore. These drawbacks also cause journal, result in double write > penalty. Could you explain me more detail about POSIX fails when using in > FileStore? and how Bluestore still guarantee consistency without journal? >From what I guess, bluestore uses the definitive storage location as a journal So, filestore: - write data to the journal - write metadata - move data from journal to definitive storage Bluestore: - write data to definitive storage (free space, not overwriting anything) - write metadata > > I find a topic on reddit that told by journal, ceph avoid buffer cache, is > it true? is is drawback of POSIX? > https://www.reddit.com/r/ceph/comments/5wbp4d/so_will_ > bluestore_make_ssd_journals_pointless/ > > 2. We have to put journal on SSD to avoid double write, but it lead to > losing some OSDs when SSD fails. With BlueStore model, we can put all WAL, > metadata, data on 1 disk, make it easily for monitoring, maintaining. But > according to this post of Sebastian Han: > https://www.sebastien-han.fr/blog/2016/05/04/Ceph-Jewel- > configure-BlueStore-with-multiple-devices/ > We could put WAL, metadata, and data on separate disks for increasing > performance, I think it is not different to FileStore model. > What is OSD deployment is most optimized? Put all on 1 disk or split on > multi disks? > > Thanks in advance > > > > _______________________________________________ > ceph-users mailing list > ceph-users@xxxxxxxxxxxxxx > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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