[Lustre-devel] question about ldlm_server_glimpse_ast

Oleg Drokin oleg.drokin at oracle.com
Fri Apr 30 11:44:43 PDT 2010


On Apr 30, 2010, at 9:00 AM, John Hammond wrote:
> I tested a patch which set rq_no_resend = 0 for glimpses, and found that 
> clients only had about 6 seconds to reply before eviction.  Since 
> eviction creates the possibility for data loss, a 6 second timeout was 
> deemed too short for production.  (With the patch applied, it was easy 
> for me to create cases where data was indeed lost.)  I was also able to 

Please note that the 6 second timeout is in fact common ldlm_timeout and it's
not just glimpses that are bound by this value.
any ldlm callbacks are required to reply withing this time, so if your
network can have delays of more then this much, you need to consider
increasing ldlm_timeout value (/proc/sys/lustre/ldlm_timeout).
On the other hand if you have a packet loss issue, even if
resending of glimpse ASTs would be present, we don't currently resend
other ASTs so the situation still has a potential for evictions
with subsequent possible data loss.


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