I saw above the recommended size for the db partition was 5% of data, but yet the recommendation is 40GB partitions for 4TB drives. Isn't that closer to 1%?
On Fri, Sep 7, 2018 at 10:06 AM, Muhammad Junaid <junaid.fsd...@gmail.com> wrote: > Thanks very much. It is clear very much now. Because we are just in > planning stage right now, would you tell me if we use 7200rpm SAS 3-4TB for > OSD's, write speed will be fine with this new scenario? Because it will > apparently writing to slower disks before actual confirmation. (I > understand there must be advantages of bluestore using direct partitions). > Regards. > > Muhammad Junaid > > On Fri, Sep 7, 2018 at 6:39 PM Richard Hesketh < > richard.hesk...@rd.bbc.co.uk> wrote: > >> It can get confusing. >> >> There will always be a WAL, and there will always be a metadata DB, for >> a bluestore OSD. However, if a separate device is not specified for the >> WAL, it is kept in the same device/partition as the DB; in the same way, >> if a separate device is not specified for the DB, it is kept on the same >> device as the actual data (an "all-in-one" OSD). Unless you have a >> separate, even faster device for the WAL to go on, you shouldn't specify >> it separately from the DB; just make one partition on your SSD per OSD, >> and make them as large as will fit together on the SSD. >> >> Also, just to be clear, the WAL is not exactly a journal in the same way >> that Filestore required a journal. Because Bluestore can provide write >> atomicity without requiring a separate journal, data is *usually* >> written directly to the longterm storage; writes are only journalled in >> the WAL to be flushed/synced later if they're below a certain size (IIRC >> 32kb by default), to avoid latency by excessive seeking on HDDs. >> >> Rich >> >> On 07/09/18 14:23, Muhammad Junaid wrote: >> > Thanks again, but sorry again too. I couldn't understand the following. >> > >> > 1. As per docs, blocks.db is used only for bluestore (file system meta >> > data info etc). It has nothing to do with actual data (for journaling) >> > which will ultimately written to slower disks. >> > 2. How will actual journaling will work if there is no WAL (As you >> > suggested)? >> > >> > Regards. >> > >> > On Fri, Sep 7, 2018 at 6:09 PM Alfredo Deza <ad...@redhat.com >> > <mailto:ad...@redhat.com>> wrote: >> > >> > On Fri, Sep 7, 2018 at 9:02 AM, Muhammad Junaid >> > <junaid.fsd...@gmail.com <mailto:junaid.fsd...@gmail.com>> wrote: >> > > Thanks Alfredo. Just to clear that My configuration has 5 OSD's >> > (7200 rpm >> > > SAS HDDS) which are slower than the 200G SSD. Thats why I asked >> > for a 10G >> > > WAL partition for each OSD on the SSD. >> > > >> > > Are you asking us to do 40GB * 5 partitions on SSD just for >> block.db? >> > >> > Yes. >> > >> > You don't need a separate WAL defined. It only makes sense when you >> > have something *faster* than where block.db will live. >> > >> > In your case 'data' will go in the slower spinning devices, >> 'block.db' >> > will go in the SSD, and there is no need for WAL. You would only >> > benefit >> > from WAL if you had another device, like an NVMe, where 2GB >> partitions >> > (or LVs) could be created for block.wal >> > >> > >> > > >> > > On Fri, Sep 7, 2018 at 5:36 PM Alfredo Deza <ad...@redhat.com >> > <mailto:ad...@redhat.com>> wrote: >> > >> >> > >> On Fri, Sep 7, 2018 at 8:27 AM, Muhammad Junaid >> > <junaid.fsd...@gmail.com <mailto:junaid.fsd...@gmail.com>> >> > >> wrote: >> > >> > Hi there >> > >> > >> > >> > Asking the questions as a newbie. May be asked a number of >> > times before >> > >> > by >> > >> > many but sorry, it is not clear yet to me. >> > >> > >> > >> > 1. The WAL device is just like journaling device used before >> > bluestore. >> > >> > And >> > >> > CEPH confirms Write to client after writing to it (Before >> > actual write >> > >> > to >> > >> > primary device)? >> > >> > >> > >> > 2. If we have lets say 5 OSD's (4 TB SAS) and 1 200GB SSD. >> > Should we >> > >> > partition SSD in 10 partitions? Shoud/Can we set WAL Partition >> Size >> > >> > against >> > >> > each OSD as 10GB? Or what min/max we should set for WAL >> > Partition? And >> > >> > can >> > >> > we set remaining 150GB as (30GB * 5) for 5 db partitions for >> > all OSD's? >> > >> >> > >> A WAL partition would only help if you have a device faster than >> the >> > >> SSD where the block.db would go. >> > >> >> > >> We recently updated our sizing recommendations for block.db at >> least >> > >> 4% of the size of block (also referenced as the data device): >> > >> >> > >> >> > >> >> > http://docs.ceph.com/docs/master/rados/configuration/ >> bluestore-config-ref/#sizing >> > >> >> > >> In your case, what you want is to create 5 logical volumes from >> your >> > >> 200GB at 40GB each, without a need for a WAL device. >> > >> >> > >> >> > >> > >> > >> > Thanks in advance. Regards. >> > >> > >> > >> > Muhammad Junaid >> > >> > >> > >> > _______________________________________________ >> > >> > 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 >> > >> >> >> _______________________________________________ >> 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
