thanks Oliver, does the journal need be committed twice? One is for write IO to the cache tier? the other is for write IO destaged to SATA backend pool?
2016-04-21 19:38 GMT+08:00 Oliver Dzombic <i...@ip-interactive.de>: > Hi, > > afaik cache does not have to do anything with journals. > > So your OSD's need journals, and for performance, you will take SSD's. > > The Cache should be something faster than your OSD's. Usually SSD or NVMe. > > The Cache is an extra Space in front of your OSD's which is supposed to > speed up things because the cache operate faster than the OSD's and the > cache will flush its content to the slower OSD's. > > So, the cache is independent from the OSD's. And this way, from their > journals. > > And, the cache >must< be on faster drives than the OSD's, otherwise you > wont see any performance increase. > > -- > Mit freundlichen Gruessen / Best regards > > Oliver Dzombic > IP-Interactive > > mailto:i...@ip-interactive.de > > Anschrift: > > IP Interactive UG ( haftungsbeschraenkt ) > Zum Sonnenberg 1-3 > 63571 Gelnhausen > > HRB 93402 beim Amtsgericht Hanau > Geschäftsführung: Oliver Dzombic > > Steuer Nr.: 35 236 3622 1 > UST ID: DE274086107 > > > Am 21.04.2016 um 13:27 schrieb min fang: > > Hi, my ceph cluster has two pools, ssd cache tier pool and SATA backend > > pool. For this configuration, do I need use SSD as journal device? I do > > not know whether cache tier take the journal role? thanks > > > > > > _______________________________________________ > > 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
