Hi John,
On 02/09/2014 05:29, Jakes John wrote:> Hi,
> I have some general questions regarding the crush map. It would be helpful
> if someone can help me out by clarifying them.
>
> 1. I saw that a bucket 'host' is always created for the crush maps which are
> automatically generated by ceph. If I am manually creating crushmap, do I
> need to always add a bucket called ' host' ? As I was looking through the
> source code, I didn't see any need for this. If not necessary, can osd's of
> the same host be split into mulitple buckets?
>
> eg : Say host 1 has four osd's- osd.0,osd.1,osd.2, osd.3
> host 2 has four osd's- osd.4,osd.5,osd.6,osd.7
>
> and create two buckets -
>
> HostGroup bucket1- {osd.0, osd.1,osd.4,osd.5}
> HostGroup bucket2-{osd.2,osd.3,osd.6,osd.7} where HostGroup is new bucket
> type instead of the default 'host' type.
>
>
> Is this configuration possible or invalid? If this is possible, I can group
> SSD's of all hosts into 1 bucket and HDD's into other.What you describe seem possible but I'm not sure what problem you are trying to solve. The crush map described at http://ceph.com/docs/master/rados/operations/crush-map/#placing-different-pools-on-different-osds is not what you want ? > 2. I have read in Ceph docs that same osd is not advised to be part of two > buckets(two pools). A single OSD should be in a single bucket in the crush map indeed. But it is common for two OSD to be part of multiple pools. The pools are associated with a ruleset and each ruleset can choose in the same set of OSDs. > Is there any reason for it? But,I couldn't find this limitation in the source > code. There is no limitation in the code but the crush function has been tested and used with a hierarchy where leaf nodes are not part of more than one bucket. Cheers > eg:osd.0 is in bucket1 and bucket2. > > Is this configuration possible or invalid? If this is possible, I have the > flexibility to have group data which are written to different pools. > > 3. Is it possible to exclude or include a particular osd/host/rack in the > crush mapping?. > > eg: I need to have third replica always in rack3 (a specified row/rack/host > based on requirements) . First two can be chosen randomly > > If possible, how can I configure it? > > > 4. It is said that osd weights must be configured based on the storage. Say > if I have SSD of 512 GB and HDD of 1 TB and if I configure .5 and 1 > respectively, am I treating both SSD and HDD equally? How do I prioritize SSD > over HDD? > > 5. Continuing from 4), If i have mix of SSD's and HDD's in the same host, > what are the best ways possible to utilize the SSD capabilities in the ceph > cluster? > > > Looking forward to your help, > > Thanks, > > > > > > > > > > _______________________________________________ > ceph-users mailing list > [email protected] > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > -- Loïc Dachary, Artisan Logiciel Libre
signature.asc
Description: OpenPGP digital signature
_______________________________________________ ceph-users mailing list [email protected] http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
