fuel-dev team mailing list archive

[Dmitry Borodaenko <dborodaenko@xxxxxxxxxxxx>]

Roman,

The Facter snippet you linked to is only responsible for detecting the
OSD Journal devices created during provisioning. Here is the logic in
the disk provisioning script to actually create journal partitions:

https://github.com/stackforge/fuel-library/blob/master/deployment/puppet/cobbler/templates/scripts/pmanager.py#L206

As you can see, pmanager will limit the size of each journal partition
to 10GB, so if your SSD is large enough to be greater than 10GB x
(number of OSD HDDs), there will be enough unallocated space left on
the SSD to create more journal partitions for new OSDs (make sure you
pass --typecode option to sgdisk with the right GPT type GUID). And if
you have more OSD drives than size of your SSD divided by 10GB, you're
better off adding another SSD or even not using dedicated journal in
the first place.

-DmitryB

On Fri, Jan 17, 2014 at 6:42 AM, Roman Sokolkov <rsokolkov@xxxxxxxxxxxx> wrote:
> Andrey,
>
>> are we able to use multiple block devices for journal purpose right now?
>
> Answer on your question is yes. I've checked it already. I've used 2 disks
> for journal and 2 for OSD. Single journal disk mapped on single OSD disk in
> this case. I assume if i will add additional (third) OSD disk, it will
> remain without separate journal. Here is the logic.
>
> But the main question was:
>
> Is there ability to use one journal disk for multiple OSD disks?
>
> i.e. i have 4 SSDs and 20 HDDs in storage node. I want to use 1 SSD per 5
> HDD. In this case SSD should contain 5 partitions.
>
> Thanks, Roman S.
>
>
> On Fri, Jan 17, 2014 at 6:31 PM, Andrey Korolev <akorolev@xxxxxxxxxxxx>
> wrote:
>>
>> Hello,
>>
>> Services team came with a question about Ceph setup - are we able to use
>> multiple block devices for journal purpose right now?
>>
>> Also I am reviving back the issue with journal placement - our current
>> approach to slice journal device to the equal chunk is not very good in
>> terms of possible reconfiguration - e.g. you can not add more OSD daemons
>> without shutting down every daemon on the selected nodes, doing journal
>> flush and repartitioning. Can we please switch to the filesystem-based
>> journal placement in the next release? Passing 'discard' option to the
>> filesystem we will be able to maintain same level of wearout and with fixed
>> or proportional journal size (e.g. to not allocate all free space) we will
>> achieve greater maintenance flexibility.
>
>
>
>
> --
> Best regards, Roman Sokolkov



-- 
Dmitry Borodaenko