An RBD can only be mapped to a single client host. There is no way around this. An RBD at its core is a block device. Connecting an RBD to 2 servers would be like connecting a harddrive to 2 servers.
On Mon, Dec 11, 2017 at 9:13 AM 13605702596 <13605702596@xxxxxxx> wrote:
hi Jasonthanks for your answer.there is one more question, that is:can we use rbd image to share data between two clients? one wirtes data, another just reads?thanks_______________________________________________At 2017-12-11 21:52:54, "Jason Dillaman" <jdillama@xxxxxxxxxx> wrote: >On Mon, Dec 11, 2017 at 7:50 AM, 13605702596@xxxxxxx ><13605702596@xxxxxxx> wrote: >> hi >> >> i'm testing on rbd image. the are TWO questions that confused me. >> ceph -v >> ceph version 10.2.10 (5dc1e4c05cb68dbf62ae6fce3f0700e4654fdbbe) >> uname -r >> 3.10.0-514.el7.x86_64 >> >> (1) does rbd image supports multiple clients to write data simultaneously? > >You would need to put a clustered file system like GFS2 on top of the >block device to utilize it concurrently. > >> if it supports, how can share data between several clients using rbd image? >> client A: write data to rbd/test >> client B: rbd map, and mount it to /mnt, file can be found in /mnt dir, but >> the content is miss. >> >> on monitor: >> rbd create rbd/test -s 1024 >> rbd info rbd/test >> rbd image 'test': >> size 1024 MB in 256 objects >> order 22 (4096 kB objects) >> block_name_prefix: rbd_data.121d238e1f29 >> format: 2 >> features: layering, exclusive-lock, object-map, fast-diff, deep-flatten >> flags: >> then i disble the feature: object-map, fast-diff, deep-flatten >> >> on client A: >> rbd map rbd/test >> mkfs -t xfs /dev/rbd0 >> mount /dev/rbd/rbd/test /mnt/ >> echo 124 > /mnt/host124 >> cat host124 >> 124 >> >> on client B: >> rbd map rbd/test >> mount /dev/rbd/rbd/test /mnt/ >> cat host124 --> show nothing! >> >> echo 125 > /mnt/host125 >> cat /mnt/host125 >> 125 >> >> then on client C: >> rbd map rbd/test >> mount /dev/rbd/rbd/test /mnt/ >> cd /mnt >> cat host124 --> show nothing! >> cat host125 --> show nothing! >> >> (2) does rbd image supports stripping? if does, howto? > >Not yet, but it's a work-in-progress for krbd to support "fancy" >striping (librbd would support it via rbd-nbd). > >> on monitor, i create an image as following: >> rbd create rbd/test --image-feature layering,striping,exclusive-lock --size >> 1024 --object-size 4096 --stripe-unit 4096 --stripe-count 2 >> stripe unit is not a factor of the object size >> rbd create rbd/test --image-feature layering,striping,exclusive-lock --size >> 1024 --object-size 8M --stripe-unit 4M --stripe-count 2 >> rbd: the argument ('4M') for option '--unit' is invalid >> i don't know why those cmd fails? > >Only Luminous and later releases support specifying the stripe unit >with B/K/M suffixes. > >> finally, i successed with the following cmd: >> rbd create rbd/test --image-feature layering,striping,exclusive-lock --size >> 1024 --object-size 8388608 --stripe-unit 4194304 --stripe-count 2 >> >> but whe i map it on client, it fails. >> the error msg: >> rbd: image test: unsupported stripe unit (got 4194304 want 8388608) >> >> best wishes >> thanks >> >> ________________________________ >> 13605702596@xxxxxxx >> >> _______________________________________________ >> ceph-users mailing list >> ceph-users@xxxxxxxxxxxxxx >> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com >> > > > >-- >Jason
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