Sorry about the misused term 'OSS: object storage server' (a term often used in Lustre filesystem), what I meant is 4 hosts, each manages 12 OSDs.
Thanks for anyone who may answer any of my questions.
Best,
Jialin
NERSC/LBNL
On Sun, Jun 17, 2018 at 11:29 AM Jialin Liu <jalnliu@xxxxxxx> wrote:
Hello,
I have a couple questions regarding the IO on OSD via librados.
1. How to check which osd is receiving data?
2. Can the write operation return immediately to the application once the write to the primary OSD is done? or does it return only when the data is replicated twice? (size=3)
3. What is the I/O size in the lower level in librados, e.g., if I send a 100MB request with 1 thread, does librados send the data by a fixed transaction size?
4. I have 4 OSS, 48 OSDs, will the 4 OSS become the bottleneck? from the ceph documentation, once the cluster map is received by the client, the client can talk to OSD directly, so the assumption is the max parallelism depends on the number of OSDs, is this correct?
Best,
Jialin
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