I'm going to hope that Igor is correct since I have a PR for DeepSea to change this exact behavior.
With respect to ceph-deploy, if you specify --block-wal, your OSD will have a block.wal symlink. Likewise, --block-db will give you a block.db symlink. If you have both on the command line, you will get both. That does work, but this also means twice the partitions to manage on a shared device. We have been doing Bluestore this way in DeepSea since we started supporting Bluestore. Recently, I learned that this is not necessary when both are on the same device. The wal for the Bluestore OSD will use the db device when set to 0. I will soon verify that also means when the block.wal is absent. Eric On Thursday, June 28, 2018 5:07:25 PM EDT Kai Wagner wrote: > I'm also not 100% sure but I think that the first one is the right way > to go. The second command only specifies the db partition but no > dedicated WAL partition. The first one should do the trick. > > On 28.06.2018 22:58, Igor Fedotov wrote: > > I think the second variant is what you need. But I'm not the guru in > > ceph-deploy so there might be some nuances there... > > > > Anyway the general idea is to have just a single NVME partition (for > > both WAL and DB) per OSD. > > > > Thanks, > > > > Igor > > > > On 6/27/2018 11:28 PM, Pardhiv Karri wrote: > >> Thank you Igor for the response. > >> > >> So do I need to use this, > >> > >> ceph-deploy osd create --debug --bluestore --data /dev/sdb > >> --block-wal /dev/nvme0n1p1 --block-db /dev/nvme0n1p2 cephdatahost1 > >> > >> or > >> > >> ceph-deploy osd create --debug --bluestore --data /dev/sdb --block-db > >> /dev/nvme0n1p2 cephdatahost1 > >> > >> where /dev/sdb is ssd disk for osd > >> /dev/nvmen0n1p1 is 10G partition > >> /dev/nvme0n1p2 is 25G partition > >> > >> > >> Thanks, > >> Pardhiv K > >> > >> On Wed, Jun 27, 2018 at 9:08 AM Igor Fedotov <ifedo...@suse.de > >> > >> <mailto:ifedo...@suse.de>> wrote: > >> Hi Pardhiv, > >> > >> there is no WalDB in Ceph. > >> > >> It's WAL (Write Ahead Log) that is a way to ensure write safety > >> in RocksDB. In other words - that's just a RocksDB subsystem > >> which can use separate volume though. > >> > >> In general For BlueStore/BlueFS one can either allocate separate > >> volumes for WAL and DB or have them on the same volume. The > >> latter is the common option. > >> > >> The separated layout makes sense when you have tiny but > >> super-fast device (for WAL) and less effective (but still fast) > >> larger drive for DB. Not to mention the third one for user data.... > >> > >> E.g. HDD (user data) + SDD (DB) + NVME (WAL) is such a layout. > >> > >> > >> So for you case IMO it's optimal to have merged WAL+DB at NVME > >> and data at SSD. Hence no need for separate WAL volume. > >> > >> > >> Regards, > >> > >> Igor > >> > >> On 6/26/2018 10:22 PM, Pardhiv Karri wrote: > >>> Hi, > >>> > >>> I am playing with Ceph Luminous and getting confused information > >>> around usage of WalDB vs RocksDB. > >>> > >>> I have 2TB NVMe drive which I want to use for Wal/Rocks DB and > >>> have 5 2TB SSD's for OSD. > >>> I am planning to create 5 30GB partitions for RocksDB on NVMe > >>> drive, do I need to create partitions of WalDB also on NVMe > >>> drive or does RocksDB does same work as WalDB plus having > >>> metadata on it? > >>> > >>> So my question is do I really need to use WalDB along with > >>> RocksDB or having RocksDB only is fine? > >>> > >>> Thanks, > >>> Pardhiv K > >>> > >>> > >>> > >>> > >>> > >>> _______________________________________________ > >>> 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 > >> > >> _______________________________________________ > >> 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 > > > > _______________________________________________ > > ceph-users mailing list > > ceph-users@lists.ceph.com > > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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