> -----Original Message----- > From: Wido den Hollander [mailto:w...@42on.com] > Sent: 22 August 2016 18:22 > To: ceph-users <ceph-users@lists.ceph.com>; n...@fisk.me.uk > Subject: Re: [ceph-users] udev rule to set readahead on Ceph RBD's > > > > Op 22 augustus 2016 om 15:17 schreef Nick Fisk <n...@fisk.me.uk>: > > > > > > Hope it's useful to someone > > > > https://gist.github.com/fiskn/6c135ab218d35e8b53ec0148fca47bf6 > > > > Thanks for sharing. Might this be worth adding it to ceph-common?
Maybe, Ilya kindly set the default for krbd to 4MB last year in the kernel, but maybe having this available would be handy if people ever want a different default. It could be set to 4MB as well, with a note somewhere to point people at its direction if they need to change it. > > And is 16MB something we should want by default or does this apply to your > situation better? It sort of applies to me. With a 4MB readahead you will probably struggle to get much more than around 50-80MB/s sequential reads, as the read ahead will only ever hit 1 object at a time. If you want to get nearer 200MB/s then you need to set either 16 or 32MB readahead. I need it to stream to LTO6 tape. Depending on what you are doing this may or may not be required. > > Wido > > > > > _______________________________________________ > > 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
