[Gluster-devel] option read-subvolume

[gordan at bobich.net]

On Fri, 30 May 2008, Josh Bowers wrote:

> I am trying to setup AFR across two nodes with the clients on the same boxes 
> as the servers. Currently, I am using "AFR single process" to do this and 
> everything seems to work.

Fascinating. I was trying the exact same setup and couldn't get it to work 
due to a bug that isn't yet fixed as of v1.3.9. Mind you I was doing AFR 
"server side" inside the single process, so that could be why it's working 
for you.

I guess I really ought to try that.

> However, I think I'm missing something because the performance seems to be 
> poor.
>
> I was under the impression that "option read-subvolume" option would read 
> from the local filesystem if the "type storage/posix" was specified for the 
> subvolume. It seems to have no affect whether or not this option is used.

Are you using big files for read testing or small ones? On each open, you 
will suffer the latency of checking the metadata on both servers (ping 
time plus overheads), but once that checks out, the file will be read off 
the read-subvolume specified.

Of course, you will still have the overhead of running fuse. To check if 
the problem is network related, disconnect the 2nd server, so the source 
has no choice but to be local and see of the performance on large file 
reads improves. If it doesn't, then it was working correctly to begin 
with.

Gordan