So why do not journal write only metadata? As I've read, it is for ensure consistency of data, but I do not know how to do that in detail? And why BlueStore still ensure consistency without journal?
2017-09-20 16:03 GMT+07:00 <c...@jack.fr.eu.org>: > 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@lists.ceph.com > > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > > > > _______________________________________________ > ceph-users mailing list > ceph-users@lists.ceph.com > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com >
_______________________________________________ ceph-users mailing list ceph-users@lists.ceph.com http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
