Am I misunderstanding cluster.read-subvolume/cluster.read-subvolume-index?
I have two regions, "A" and "B" with servers "a" and "b" in,
respectfully, each region. I have clients in both regions. Intra-region
communication is fast, but the pipe between the regions is terrible.
I'd like to minimize inter-region communication to as close to glusterfs
write operations only and have reads go to the server in the region the
client is running in.
I have created a replica volume as:
gluster volume create gv0 replica 2 a:/data/brick1/gv0
b:/data/brick1/gv0 force
As a baseline, if I use scp to copy from the brick directly, I get --
for a 100M file -- times of about 6s if the client scps from the server
in the same region and anywhere from 3 to 5 minutes if I the client scps
the server in the other region.
I was under the impression (from something I read but can't now find)
that glusterfs automatically picks the fastest replica, but that has not
been my experience; glusterfs seems to generally prefer the server in
the other region over the "local" one, with times usually in excess of 4
minutes.
I've also tried having clients mount the volume using the "xlator"
options cluster.read-subvolume and cluster.read-subvolume-index, but
neither seem to have any impact. Here are sample mount commands to show
what I'm attempting:
mount -t glusterfs -o xlator-option=cluster.read-subvolume=gv0-client-<0
or 1> a:/gv0 /mnt/glusterfs
mount -t glusterfs -o xlator-option=cluster.read-subvolume-index=<0 or
1> a:/gv0 /mnt/glusterfs
Am I misunderstanding how glusterfs works, particularly when trying to
"read locally"? Is it possible to configure glusterfs to use a local
replica (or the "fastest replica") for reads?
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