Dear All,
First of all, this is my first post, so please be lenient :)
For the last few days I have been testing ceph, and cephfs, deploying a
PoC cluster.
I have been testing the cephfs kernel client caching, when I came across
something strange, and I cannot decide if it is a bug or I just messed
up something.
Steps given client1 and client2 both mounded the same cephfs, extra
mount option, noatime:
Client 1: watch -n 1 ls -lah /mnt/cephfs
-in tcpdump I can see that the directory is being listed once and only
once, all the following ls requests are served from the client cache
Client 2: make any modification for example append to a file, or delete
a file directly under /mnt/cephfs
-The operation is done, and client1 is informed about the change OK.
-Client1 does not seem to cache the new metadata information received
from the metadata server, now it communicates every second with the mds.
Client 1: stop watch ls... command, wait a few sec and restart it
-The communication stops, client1 serves ls data from cache
Please help, if it is intentional then why, if not, how can I debug it?
Where can I find documentation about the kernel client and it's caching
strategy?
Thank You!
------------
Ceph cluster version: Luminous on all nodes
Client: tested on ubuntu xential - 4.4.0-96-generic #119-Ubuntu - all
settings default, except noatime
Client: tested on Fedora 26 - 4.13.5-200.fc26.x86_64+debug - all
settings default, except noatime
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