Hey folks, 

We've been running VM's on qemu using a replicated gluster volume connecting 
using gfapi and things have been going well for the most part. Something we've 
noticed though is that we have problems with many concurrent disk operations 
and disk latency. The latency gets bad enough that the process eats the cpu and 
the entire machine stalls. The place where we've seen it the worst is a apache2 
server under very high load which had to be converted to raw disk image due to 
performance issues. The hypervisors are connected directly to each other over a 
bonded pair of 10Gb fiber modules and are the only bricks in the volume. Volume 
info is 



Volume Name: VMARRAY 
Type: Replicate 
Volume ID: 67b3ad79-4b48-4597-9433-47063f90a7a0 
Status: Started 
Number of Bricks: 1 x 2 = 2 
Transport-type: tcp 
Bricks: 
Brick1: 10.9.1.1:/mnt/xfs/VMARRAY 
Brick2: 10.9.1.2:/mnt/xfs/VMARRAY 
Options Reconfigured: 
nfs.disable: on 
network.ping-timeout: 7 
cluster.eager-lock: on 
performance.flush-behind: on 
performance.write-behind: on 
performance.write-behind-window-size: 4MB 
performance.cache-size: 1GB 
server.allow-insecure: on 
diagnostics.client-log-level: ERROR 




Any advice for performance improvements for high IO / low bandwidth tuning 
would be appreciated. 




Thanks, 

Josh 

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