use striping feature

use striping feature

[Stefan Priebe - Profihost AG]

Hello list,

is the following syntax to use the new rbd v2 striping feature correct?

rbd create -p kvmstor --format 2 --size 32000 --stripe-count 8 
--stripe-unit 131072 -s 1048576 $imagename

Idea is to have 8 stripes per 1MB object size. Or are there any other 
recommondations regarding striping?

I'm a bit confused cause rbd info shows stripe-count as bytes?

rbd image 'vm-113-disk-4':
         size 1024 GB in 262144 objects
         order 22 (4096 KB objects)
         block_name_prefix: rbd_data.d0f7639a214d
         format: 2
         features: layering
         stripe unit: 128 KB
         stripe count: 8 bytes

Stefan

Re: use striping feature

[Josh Durgin]

On 11/05/2012 04:03 AM, Stefan Priebe - Profihost AG wrote:
> Hello list,
>
> is the following syntax to use the new rbd v2 striping feature correct?
>
> rbd create -p kvmstor --format 2 --size 32000 --stripe-count 8
> --stripe-unit 131072 -s 1048576 $imagename
>
> Idea is to have 8 stripes per 1MB object size. Or are there any other
> recommondations regarding striping?

The stripe count is actually how many objects to stripe over before
repeating back to the first one. It's the number of objects in an
'object set' in the diagram at the bottom of:

http://ceph.com/docs/master/dev/file-striping/

I don't think we've done enough benchmarks to know what the best
settings are, but generally having large (like 4MB) objects
and smaller stripe units will at least help small sequential I/O.

> I'm a bit confused cause rbd info shows stripe-count as bytes?

It's not actually bytes. Sage just fixed that output in the master
branch.

Josh