[Sheepdog] sheepdog's recovery alogorithm questions

[jidalyg_8711]

Hi, Kazutaka, 

After reading the source code of the sheepdog, I have some questions confused.

1. sheepdog claim it is strong consistent, And I think the implemention of the read_object() write_object() remove_object()  ensure that strong consistent?  any other places to ensure it ?   How about it affect the performance of the sheepdog?

2. About the recovery alogorithm, When the new node join  or the node left,  sheepdog will call start_recovery()func and recovery in background. The main actions of the recovery is move the object to the new node and the epoch directory ; while recoverying, the READ_OBJECT request arrived, currently sys->epoch has increased, but the object maybe still in old epoch directory ,not yet move to the new epoch, How the sheepdog handle the situation ?  And the sys->epoch increased in update_cluster_status() before calling start_recovery()


Thanks~
yaornli
2011-03-15 



jidalyg_8711 
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