On 12/12/2014 12:48 PM, Max Power wrote: > I am new to Ceph and start discovering its features. I used ext4 partitions > (also mounted with -o discard) to place several osd on them. Then I created an > erasure coded pool in this cluster. On top of this there is the rados block > device which holds also an ext4 filesystem (of course mounted with -o > discard). >
How are you using Ceph, Kernel RBD, Qemu/KVM? > I started to create some random 1MB files with tempfile and /dev/urandom to > mess > the filesystem up and use all available space (256MB on my testdrive). After > this I deleted everything again. To my surprise the discard-feature did not > work. Ceph reports that ~256MB are used for data (after mkfs it was around > 0MB). > I also tried to use 'fstrim' on the mountpoint but it reports that "the > discard > operation is not supported". But why? > It depends. Kernel RBD does not support discard/trim yet. Qemu does under certain situations and with special configuration. A search should tell you the parameters. > It would be great to shrink the used space. Is there a way to achieve this? Or > have I done something wrong? In a professional environment you may can live > with > filesystems that only grow. But on my small home-cluster this really is a > problem. > > Greetings from Germany! > > P.S.: I use ceph version 0.80.7 as delivered with debian jessie. > _______________________________________________ > ceph-users mailing list > ceph-users@lists.ceph.com > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > -- Wido den Hollander Ceph consultant and trainer 42on B.V. Phone: +31 (0)20 700 9902 Skype: contact42on _______________________________________________ ceph-users mailing list ceph-users@lists.ceph.com http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
