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" <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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