On 01/03/2013 01:29 PM, emyr.james wrote:
Hi,
I'm thinking of starting to use ceph initially for evaluation...seeing
how it compares to our existing lustre file system.
One thing that I would like confirmation of is how ceph stores large
files. If I store a large file in CephFS is it automatically split up
into chunks with the various chunks stored and replicated automatically
across the whole cluster, or does it store the whole file as one object
on one individial OSD and then has individual replicants of the whole
file on a small number of other OSD's ? What is the typical block size
used if files are split up....can this be configured ?
Files are by default striped in 4MB blocks which are then distributed
over the OSDS and replicated.
A 1G file will thus result in 256 different object distributed and
replicated through your cluster.
You can configure the stripe-size with the "cephfs" tool on a client.
Note: CephFS hasn't got the attention like RADOS and RBD got, so you
might run into some weird situations.
Wido
Regards,
Emyr
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