Big Thanks Ilya, for explanation 2015-11-30 22:15 GMT+03:00 Ilya Dryomov <idryo...@gmail.com>: > On Mon, Nov 30, 2015 at 7:47 PM, Timofey Titovets <nefelim...@gmail.com> > wrote: >> >> On 30 Nov 2015 21:19, "Ilya Dryomov" <idryo...@gmail.com> wrote: >>> >>> On Mon, Nov 30, 2015 at 7:17 PM, Timofey Titovets <nefelim...@gmail.com> >>> wrote: >>> > Hi list, >>> > Short: >>> > i just want ask, why i can't do: >>> > echo 129 > /sys/class/block/rbdX/queue/nr_requests >>> > >>> > i.e. why i can't set value greater then 128? >>> > Why such a restriction? >>> > >>> > Long: >>> > Usage example: >>> > i have slow CEPH HDD based storage and i want it export by iSCSI proxy >>> > machine for ESXi cluster >>> > >>> > If i have so low queue depth, i just worry to get a performance >>> > problem because cluster can process request, but HV/VM can't send new >>> > request if queue in full state >>> > >>> > Then i have two solutions make several RBD devices for exporting or >>> > increase queue depth. >>> > >>> > What you think about it? >>> >>> Which kernel is that? >>> >>> Thanks, >>> >>> Ilya >> >> 4.2.5 on archlinux, >> Thanks > > On 4.2 and above you can set queue depth at map time: > > # rbd map -o queue_depth=129 ... > > The reasons lie in the block layer, which has to support both single > queue drivers and drivers that are using blk-mq interface. There are > data structures that have to be preallocated on device setup, etc. > nr_requests setting just doesn't work for blk-mq devices. > > Thanks, > > Ilya
-- Have a nice day, Timofey. _______________________________________________ ceph-users mailing list ceph-users@lists.ceph.com http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
