----- Original Message ----- > From: "Lindsay Mathieson" <lindsay.mathieson@xxxxxxxxx> > To: "gluster-users" <gluster-users@xxxxxxxxxxx> > Sent: Monday, November 3, 2014 12:41:59 AM > Subject: iowait issues > > Using glusterfs (2 nodes, one disk each, replicated) to serve up my > kvm disk images. Wehn 4+ vm's are running, I'm seeing iowait upto 25%, > which is causing problems. > > Oddly my nas, which has crappy network performance compared to the > gluster cluster doesn't display this problem, but it does use a RAID10 > array. > > Would my iowait problems because by the gluster network replication or > by the single disks (WD Red 3TB). > > If the latter, would adding a ssd cache help? something else? What is you NW bandwidth? If you are using gigabit then I can see this as the problem. I have found that without at very least 20 MB / sec of throughput per VM they get difficult to use with a GUI. So with gigabit and replication: Gigabit = 120 MB / sec, divide that by 2 for replication: 60 MB / sec / 4 VMs = 15 MB / sec per VM That is under the at least 20 that I like to see. With gluster you are using 1/2 you bandwidth for replication and with the NAS you are probably getting the full gigabit. Also having the RAID on the NAS defiantly helps, but I think in this case you are probably hitting the NIC as the bottleneck. I would look at NW bandwith first and then look at RAID, you need to have a fast enough back end to service the bandwidth of your NICs. Also the more spindles you have the better IOPS / smallfile / random IO will be. What about 10G NW cards or NIC bonding? How many VMs are you looking to run? What sort of workload? -b > thanks, > > -- > Lindsay > _______________________________________________ > Gluster-users mailing list > Gluster-users@xxxxxxxxxxx > http://supercolony.gluster.org/mailman/listinfo/gluster-users > _______________________________________________ Gluster-users mailing list Gluster-users@xxxxxxxxxxx http://supercolony.gluster.org/mailman/listinfo/gluster-users
