[ceph-users] How Rados gateway stripes and combines object data

Wido den Hollander wido at 42on.com
Thu Nov 23 00:15:36 PST 2017


> Op 23 november 2017 om 7:43 schreef Prasad Bhalerao <prasadbhalerao1983 at gmail.com>:
> 
> 
> Hi,
> 
> I am new to CEPH and I have some question regarding it?
> 
> Could you please help out?
> 

Yes, but keep in mind a lot of these questions have been answered previously.

> What is default value of rgw_stripe_size and max_chunk_size?
> 

RGW stripes in 4MB RADOS objects.

> What is default size of object stored in Ceph Storage Cluster? Is it
> dependent on stripe size or chunk size?
> 

None, the application on top of RADOS decides how large the stripes are.

> What is bucket with respect to RGW? How one should decide the name of
> bucket? Does creating too many bucket (different bucket per request)
> creates performance problem?
> 

Please refer to the Amazon S3 model, that will explain what buckets are.

You can create millions of buckets without having a performance impact.

> Why does CEPH first stripes the data into series of stripes and then again
> divide these stripes into smaller chunks? Is striping data into stripes not
> enough?
> 

It doesn't. RGW stripes over RADOS, RADOS itself doesn't stripe data.

> If an object is divided into series of smaller units (for performance
> benefit) , how does CEPH returns the complete object when GET request is
> made?
> 
> Where does it store the ids/numbers of subsequent stripes to form a
> complete object from its smaller chunks?
> 
> Does striping a small object (e.g. 100 KB to 4 MB) creates a performance
> overhead as CEPH has to read all the chunks related to this Object and then
> combine it into one single object before it returns it? Isn't it too much
> optimization for handling smaller objects?
> 
> Does librados (ceph native apis) also perform data striping if used for
> storing data into CEPH cluster?
> 

No, RADOS itself does not stripe objects.

Wido

> Thanks,
> Prasad
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