[Gluster-users] How does gluster identify which brick is the closest

[Thai. Ngo Bao]

Hello all,

First of all, I would like to thank you for the great FS. I have some basic questions regarding Elastic Hash Algorithm (EHA).

I understand that EHA decides data placement at a host level and then places complete files on its selected storage. EHA also takes one step further and optimizes selection based not just on availability, but performance as well. Thus, if there is a copy of the file that is closer to the user, the closest copy is used.

So my questions are: How does gluster identify where the closest copy is? How does gluster identify which brick storing the copy closest to user? Which bricks are in a same or different subnets? Which value(s) does gluster take to compare for that purpose? Are they dynamic values, the results of EHA? Also, please point me out where is the code segments/modules of gluster doing these jobs.

I appreciate your time, and thank you in advance.

Regards,
Thai Ngo