Hi Am 27. Januar 2019 18:20:24 MEZ schrieb Will Dennis <wdennis@xxxxxxxxxxxx>: >Been reading "Learning Ceph - Second Edition" >(https://learning.oreilly.com/library/view/learning-ceph-/9781787127913/8f98bac7-44d4-45dc-b672-447d162ea604.xhtml) >and in Ch. 4 I read this: > >"We've noted that Ceph OSDs built with the new BlueStore back end do >not require journals. One might reason that additional cost savings can >be had by not having to deploy journal devices, and this can be quite >true. However, BlueStore does still benefit from provisioning certain >data components on faster storage, especially when OSDs are deployed on >relatively slow HDDs. Today's investment in fast FileStore journal >devices for HDD OSDs is not wasted when migrating to BlueStore. When >repaving OSDs as BlueStore devices the former journal devices can be >readily re purposed for BlueStore's RocksDB and WAL data. When using >SSD-based OSDs, this BlueStore accessory data can reasonably be >colocated with the OSD data store. For even better performance they can >employ faster yet NVMe or other technloogies for WAL and RocksDB. This >approach is not unknown for traditional FileStore journals as well, >though it is not inexpensive.Ceph clusters that are fortunate to >exploit SSDs as primary OSD dri >ves usually do not require discrete journal devices, though use cases >that require every last bit of performance may justify NVMe journals. >SSD clusters with NVMe journals are as uncommon as they are expensive, >but they are not unknown." > >So can I get by with using a single SATA SSD (size?) per server for >RocksDB / WAL if I'm using Bluestore? IIRC there is a rule of thump where the Size of DB-partition should be 4% of the OSD Size. I.e. 4TB OSD should have At least a DB Partition of 160GB Hth - Mehmet > > >> - Is putting the journal on a partition of the SATA drives a real I/O >killer? (this is how my Proxmox boxes are set up) >> - If YES to the above, then is a SATA SSD acceptable for journal >device, or should I definitely consider PCIe SSD? (I'd have to limit to >one per server, which I know isn't optimal, but price prevents >otherwise...) >_______________________________________________ >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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