On Wed, Jul 1, 2015 at 4:50 AM, Steffen Tilsch <steffen.tilsch@xxxxxxxxx> wrote: > Hello Cephers, > > I got some questions regarding where what type of IO is generated. > > > > As far as I understand it looks like this (please see picture: > http://imageshack.com/a/img673/4563/zctaGA.jpg ) : > > 1. Clients -> OSD (Journal): > > - Is it sequential write? yes > > - Is it parallel due to the many open sockets? Client IO is pg-parallel in pg layer, and is batched to journal within one thread. At last, io is also pg-parallel to writeback > > 2. OSD journal flush -> Filestore: > > - Is it periodic sequential write? it depends on client workload, mostly are not perfect seq write. > > - Is it done in parallel to the Filestore or just with one writer? > > 3. OSD -> Clients: > > - Is it parallel random read (due to distribution of objects to PGs over > many OSD's)? mostly yes > > - Is any reading (from client side) done from journals? no > > > > How is the writing to the journal done? Is it like a ringbuffer - every new > block is added to the end of the journal so that there is no "overwriting" > in the middle of the journal (that would force the head of the HDD (if not > SSD) to seek? yes, a loopback mode > > > > It would be nice if you would correct me if anything is wrong here. > > > > Thanks in advance, > > Steffen > > > _______________________________________________ > ceph-users mailing list > ceph-users@xxxxxxxxxxxxxx > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > -- Best Regards, Wheat _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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