AFR load-balancing (was:Re: [Gluster-devel] Full bore.)

[Székelyi Szabolcs]

Krishna Srinivas wrote:
> load balancing is checked-in in the latest patch 562, but i have not tested
> it for performance. you can give "option read-schedule on/off" in
> afr volume, by default it is on. If it is off, reads are done from first
> child (the way it was done before)

IMHO the default should be off, so after upgrading, you get the same
behavior with the same config file.

> But we were thinking "option read-node" would be better than
> "option read-schedule on/off"
> 
> "option read-node <sobvol>" will read from that particular subvol
> (this will help when that subvol is local storage)
> "option read-node *" will load balance from all children.
> So option is either * or one of the subvols.
> default is "option read-node *"
> What do you think about it?

What about explicitly listing the subvolumes to perform load-balancing
between? For example, "option read-nodes child1 child3" could cause AFR
to load-balance reads between child1 and child3, while writing to all
its children (child[1-3], say). The default option could be to read from
the first child. "option read-nodes *" could still mean to use all
subvolumes.

What about defining schedulers to decide which child to read from,
similar to unify file placement schedulers? Or even re-using the same
schedulers here? ;-)

Cheers, and thanks for the feature, we were excited to have it.

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