Some of this thread seems to contradict the documentation and confuses me. Is the statement below correct?
"The BlueStore journal will always be placed on the fastest device available, so using a DB device will provide the same benefit that the WAL device would while also allowing additional metadata to be stored there (if it will fix)." http://docs.ceph.com/docs/master/rados/configuration/bluestore-config-ref/#devices it seems to be saying that there's no reason to create separate WAL and DB partitions if they are on the same device. Specifying one large DB partition per OSD will cover both uses. thanks, Ben On Thu, Sep 21, 2017 at 12:15 PM, Dietmar Rieder <dietmar.rie...@i-med.ac.at> wrote: > On 09/21/2017 05:03 PM, Mark Nelson wrote: >> >> >> On 09/21/2017 03:17 AM, Dietmar Rieder wrote: >>> On 09/21/2017 09:45 AM, Maged Mokhtar wrote: >>>> On 2017-09-21 07:56, Lazuardi Nasution wrote: >>>> >>>>> Hi, >>>>> >>>>> I'm still looking for the answer of these questions. Maybe someone can >>>>> share their thought on these. Any comment will be helpful too. >>>>> >>>>> Best regards, >>>>> >>>>> On Sat, Sep 16, 2017 at 1:39 AM, Lazuardi Nasution >>>>> <mrxlazuar...@gmail.com <mailto:mrxlazuar...@gmail.com>> wrote: >>>>> >>>>> Hi, >>>>> >>>>> 1. Is it possible configure use osd_data not as small partition on >>>>> OSD but a folder (ex. on root disk)? If yes, how to do that with >>>>> ceph-disk and any pros/cons of doing that? >>>>> 2. Is WAL & DB size calculated based on OSD size or expected >>>>> throughput like on journal device of filestore? If no, what is the >>>>> default value and pro/cons of adjusting that? >>>>> 3. Is partition alignment matter on Bluestore, including WAL & DB >>>>> if using separate device for them? >>>>> >>>>> Best regards, >>>>> >>>>> >>>>> _______________________________________________ >>>>> 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 >>>> >>>> >>>> >>>> I am also looking for recommendations on wal/db partition sizes. Some >>>> hints: >>>> >>>> ceph-disk defaults used in case it does not find >>>> bluestore_block_wal_size or bluestore_block_db_size in config file: >>>> >>>> wal = 512MB >>>> >>>> db = if bluestore_block_size (data size) is in config file it uses 1/100 >>>> of it else it uses 1G. >>>> >>>> There is also a presentation by Sage back in March, see page 16: >>>> >>>> https://www.slideshare.net/sageweil1/bluestore-a-new-storage-backend-for-ceph-one-year-in >>>> >>>> >>>> wal: 512 MB >>>> >>>> db: "a few" GB >>>> >>>> the wal size is probably not debatable, it will be like a journal for >>>> small block sizes which are constrained by iops hence 512 MB is more >>>> than enough. Probably we will see more on the db size in the future. >>> >>> This is what I understood so far. >>> I wonder if it makes sense to set the db size as big as possible and >>> divide entire db device is by the number of OSDs it will serve. >>> >>> E.g. 10 OSDs / 1 NVME (800GB) >>> >>> (800GB - 10x1GB wal ) / 10 = ~79Gb db size per OSD >>> >>> Is this smart/stupid? >> >> Personally I'd use 512MB-2GB for the WAL (larger buffers reduce write >> amp but mean larger memtables and potentially higher overhead scanning >> through memtables). 4x256MB buffers works pretty well, but it means >> memory overhead too. Beyond that, I'd devote the entire rest of the >> device to DB partitions. >> > > thanks for your suggestion Mark! > > So, just to make sure I understood this right: > > You'd use a separeate 512MB-2GB WAL partition for each OSD and the > entire rest for DB partitions. > > In the example case with 10xHDD OSD and 1 NVME it would then be 10 WAL > partitions with each 512MB-2GB and 10 equal sized DB partitions > consuming the rest of the NVME. > > > Thanks > Dietmar > -- > _________________________________________ > D i e t m a r R i e d e r, Mag.Dr. > Innsbruck Medical University > Biocenter - Division for Bioinformatics > > > > _______________________________________________ > 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
