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 <13605702...@163.com> wrote:
> hi Jason
> thanks 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" <jdill...@redhat.com> wrote:
> >On Mon, Dec 11, 2017 at 7:50 AM, 13605702...@163.com
> ><13605702...@163.com> 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
> >>
> >> ________________________________
> >> 13605702...@163.com
> >>
> >> _______________________________________________
> >> ceph-users mailing list
> >> ceph-users@lists.ceph.com
> >> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
> >>
> >
> >
> >
> >--
> >Jason
>
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