Re: how to debug slow rbd block device

[Josh Durgin <josh.durgin@inktank.com>]

On 05/23/2012 01:20 AM, Stefan Priebe - Profihost AG wrote:
> Am 23.05.2012 09:19, schrieb Josh Durgin:
>> On 05/23/2012 12:01 AM, Stefan Priebe - Profihost AG wrote:
>>> Am 23.05.2012 08:30, schrieb Josh Durgin:
>>>> On 05/22/2012 11:18 PM, Stefan Priebe - Profihost AG wrote:
>>>>> Hi,
>>>>>
>>>>>>> So try enabling RBD writeback caching — see http://marc.info
>>>>>>> /?l=ceph-devel&m=133758599712768&w=2
>>>>>>> will test tomorrow. Thanks.
>>>>> Can we path this to the qemu-drive option?
>>>>
>>>> Yup, see
>>>> http://article.gmane.org/gmane.comp.file-systems.ceph.devel/6400
>>> I'm sorry, i still don't get it where to pass rbd_cache_max_dirty, ...
>>> can i add it just to the ceph.conf? Even with qemu 1.0?
>>
>> You can use any of the rbd-specific options (like rbd_cache_max_dirty)
>> with qemu>= 0.15.
>>
>> You can set them in a global ceph.conf file, or specify them on the qemu
>> command line like:
>>
>> qemu -m 512 -drive
>> file=rbd:pool/image:rbd_cache_max_dirty=0:rbd_cache=true,format=raw,if=virtio
>
> So this is enough for testing on kvm host?
>
> /etc/ceph/ceph.conf
>
> [global]
>          auth supported = cephx
>          keyring = /etc/ceph/$name.keyring
>          rbd_cache = true
>          rbd_cache_size = 32M

This should be a number in bytes - M/G/k/etc aren't parsed. Assuming you 
have the monitors listed below, this is fine. If you're not using the 
admin user, you'll need to add :id=name to the -drive string - it can't 
be set in the config file.

>          rbd_cache_max_age = 2.0
>
> ...
>
> Stefan

--
To unsubscribe from this list: send the line "unsubscribe ceph-devel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html