OK,
I found this nice page: http://ceph.com/docs/next/dev/file-striping/
which explains "--stripe_unit --stripe_count --object_size"
But still I'm not sure about
(1) what is the equivalent command on cephfs to 'rbd create --order 16' ?
(2) how to use those parameters to achieve different optimized layouts on
CephFS directories
(e.g. for streaming, small sequential IOs, small random IOs)
-Dieter
On Fri, Aug 09, 2013 at 09:44:57AM +0200, Kasper Dieter wrote:
> Hi,
>
> my goal is to set the 'object size' used in the distribution inside rados
> in an equal (or similar) way between RBD and CephFS.
>
> To set obj_size=64k in RBD I use the command:
> rbd create --size 1024000 --pool SSD-r2 ssd2-1T-64k --order 16
>
> On cephfs set_layout '-s 65536' runs into EINVAL:
> cephfs /mnt/cephfs/fio-64k/ set_layout -p 3 -s 65536 -u 4194304 -c 1
> Error setting layout: Invalid argument
>
> cephfs /mnt/cephfs/fio-64k/ set_layout -p 3 -s 65536 -u 65536 -c 1
> cephfs /mnt/cephfs/fio-64k/ show_layout
> layout.data_pool: 3
> layout.object_size: 65536
> layout.stripe_unit: 65536
> layout.stripe_count: 1
>
> The man page of cephfs says
> ---snip---
> -u --stripe_unit
> Set the size of each stripe
>
> -c --stripe_count
> Set the number of objects to stripe across
>
> -s --object_size
> Set the size of the objects to stripe across
> ---snip---
>
> What is the equivalent command on cephfs to 'rbd create --order 16' ?
> Can you please give same explanation how "--stripe_unit --stripe_count
> --object_size"
> should be used in combination to achieve different layouts on CephFS
> directories
> (e.g. optimized for streaming, small sequential IOs, small random IOs)
> ?
>
> Thanks,
> -Dieter
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