Re: cephfs set_layout - EINVAL - solved

[Kasper Dieter <dieter.kasper@ts.fujitsu.com>]

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