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
>
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>
--
Jason
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