[Lustre-discuss] Lustre & SQLite

[Michal Wesolowski]

Thanks Oleg !

I have subquestion regarding locking performance, please see below.

Oleg Drokin wrote:
> Hello!
> 
> On Feb 12, 2009, at 2:10 AM, Michal Wesolowski wrote:
>> My interpretation of Lustre documentation was that flock/localflock 
>> implements only mandatory locks.
> 
> There is no such thing as posix mandatory locking, I think.
> The existing mandatory locking depends on a combination of advisory 
> locking and kernel support in
> interpretation of a special file mode set.
> 
>> So I assume statement in Lustre Manula (ver. 15, page 16-1):
>> Note – Advisory fcntl/flock/lockf locks will be available in Lustre 1.8.
>> is a documentation bug, isn't it?
> 
> Yes, this is somewhat outdated.
> 1.6.6 and above have posix advisory locking working (though performance 
> is not ideal,
> especially if you have many clients doing a lot of locks on the same 
> file at the same
> time).
Do you mean file locking mechanism in Lustre doesn't perform as efficiently as 
on local system or is not yet optimized? Or is there any general impact on 
Lustre when at least one node has flock option turned on? For example additional 
burden on MDS or OSSes which results in lower IO/s performance.

Regards

Michal