[ovirt-users] Tuning Gluster Writes

I have 8 machines acting as gluster servers. They each have 12 drives raid 50'd together (3 sets of 4 drives raid 5'd then 0'd together as one). They connect to the compute hosts and to each other over lacp'd 10GB connections split across two cisco nexus switched with VPC. Gluster has the following set. performance.write-behind-window-size: 4MB performance.flush-behind: on performance.stat-prefetch: on server.event-threads: 4 client.event-threads: 8 performance.io-thread-count: 32 network.ping-timeout: 30 cluster.granular-entry-heal: enable performance.strict-o-direct: on storage.owner-gid: 36 storage.owner-uid: 36 features.shard: on cluster.shd-wait-qlength: 10000 cluster.shd-max-threads: 8 cluster.locking-scheme: granular cluster.data-self-heal-algorithm: full cluster.server-quorum-type: server cluster.quorum-type: auto cluster.eager-lock: enable network.remote-dio: off performance.low-prio-threads: 32 performance.io-cache: off performance.read-ahead: off performance.quick-read: off auth.allow: * user.cifs: off transport.address-family: inet nfs.disable: off performance.client-io-threads: on I have the following sysctl values on gluster client and servers, using libgfapi, MTU 9K net.core.rmem_max = 134217728 net.core.wmem_max = 134217728 net.ipv4.tcp_rmem = 4096 87380 134217728 net.ipv4.tcp_wmem = 4096 65536 134217728 net.core.netdev_max_backlog = 300000 net.ipv4.tcp_moderate_rcvbuf =1 net.ipv4.tcp_no_metrics_save = 1 net.ipv4.tcp_congestion_control=htcp reads with this setup are perfect, benchmarked in VM to be about 770MB/s sequential with disk access times of < 1ms. Writes on the other hand are all over the place. They peak around 320MB/s sequential write, which is what i expect but it seems as if there is some blocking going on. During the write test i will hit 320MB/s briefly, then 0MB/s as disk access time shoot to over 3000ms, then back to 320MB/s. It averages out to about 110MB/s afterwards. Gluster version is 3.12.15 ovirt is 4.2.7.5 Any ideas on what i could tune to eliminate or minimize that blocking?