[Lustre-discuss] Questions about MDS flow

[Jianwei Liao]

Dear all,
Though I have read the lustre manual roughly, but i am wondering about 
the MDS operation flow:
1) Clients get the layout and capabilities from MDS, then do IO 
operation. While the client modify the stripes, then the modification 
time(Mtime) should be updated. Who(clients or OSSs) and When(after 
closing the file or after the modification ) does send the update 
request to MDS.

2) I have read several documents, but about unlinking a file, after 
unlinking all stripes, who does send the message about all stripe have 
been unlinked. One says, it is the clients who want to delte that 
file(in the manual), but another one says, it is the OSTs(in Xyratex 
Lustre Architecture Priorities Overview)?

3) During the creation, the MDS may ask the OSSs to allocation the 
available stripes, then the clients can write or append the data. But 
who does keep the information of available space in the stripe? For 
example, while all stripe are used up, so, another new stripe(or 
stripes) is needed, how do things go in this situation? (first who find 
there is no available space, and then send request to MDS to allocation 
a new stripe?)

4) Is the opened_file list kept in the acitve MDS' memory?

Maybe the description is involoved, does anyone give me some hints.
Thank you very much,

Best regards,
Liao