[Gluster-users] Question on file reads from a distributed replicated volume

[Krutika Dhananjay]

----- Original Message -----

> From: "Bharathram Sivasubramanian" <Bharathram.Sivasubramanian at vantrix.com>
> To: Gluster-users at gluster.org
> Sent: Saturday, April 11, 2015 3:03:48 AM
> Subject: [Gluster-users] Question on file reads from a distributed replicated
> volume

> Let us assume that we have a distributed replicated gluster volume with 4
> bricks. Brick 1 is replicating its data with Brick 2 and Brick 3 is
> replicating its data with Brick 4. Suppose a file called aa.txt is present
> and replicated on Bricks 1 & 2. A gluster client would like to read this
> file. Which brick will the file come from? In other words:

> - Will the file always be fetched from brick 1?

> - Will the file always be fetched from brick 2?

> - Will the file be fetched from brick 1 or 2 depending on the attempt? i.e.
> is there some load balancing where sometimes the file comes from brick 1 and
> at other times the file will come from brick 2?

A given file will consistently be "read" from one of the N (in this case 2) replicas, as long as it holds a good copy of the file (that which does not need heal), even with client restart. We call it the "read child" of the file. Load balancing within a volume is done across different files wherein different files would have different but constant read children. 

-Krutika 

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