10.2. Improving Network Performance

The performance of the network can be critical when replicating data. The information transferred over the network contains the full content of the THL in addition to a small protocol overhead. Improving your network performance can have a significant impact on the overall performance of the replication process.

The following network parameters should be configured within your /etc/sysctl.conf and can safely applied to all the hosts within your cluster deployments:

# Increase size of file handles and inode cache 
fs.file-max = 2097152 

# tells the kernel how many TCP sockets that are not attached to any
# user file handle to maintain. In case this number is exceeded,
# orphaned connections are immediately reset and a warning is printed.
net.ipv4.tcp_max_orphans = 60000

# Do not cache metrics on closing connections 
net.ipv4.tcp_no_metrics_save = 1 

# Turn on window scaling which can enlarge the transfer window: 
net.ipv4.tcp_window_scaling = 1 

# Enable timestamps as defined in RFC1323: 
net.ipv4.tcp_timestamps = 1 

# Enable select acknowledgments: 
net.ipv4.tcp_sack = 1 

# Maximum number of remembered connection requests, which did not yet
# receive an acknowledgment from connecting client.
net.ipv4.tcp_max_syn_backlog = 10240

# recommended default congestion control is htcp 
net.ipv4.tcp_congestion_control=htcp 

# recommended for hosts with jumbo frames enabled 
net.ipv4.tcp_mtu_probing=1 

# Number of times SYNACKs for passive TCP connection. 
net.ipv4.tcp_synack_retries = 2 

# Allowed local port range 
net.ipv4.ip_local_port_range = 1024 65535 

# Protect Against TCP Time-Wait 
net.ipv4.tcp_rfc1337 = 1 

# Decrease the time default value for tcp_fin_timeout connection 
net.ipv4.tcp_fin_timeout = 15 

# Increase number of incoming connections 
# somaxconn defines the number of request_sock structures 
# allocated per each listen call. The
# queue is persistent through the life of the listen socket.
net.core.somaxconn = 1024

# Increase number of incoming connections backlog queue 
# Sets the maximum number of packets, queued on the INPUT 
# side, when the interface receives packets faster than
# kernel can process them. 
net.core.netdev_max_backlog = 65536 

# Increase the maximum amount of option memory buffers 
net.core.optmem_max = 25165824 

# Increase the maximum total buffer-space allocatable 
# This is measured in units of pages (4096 bytes) 
net.ipv4.tcp_mem = 65536 131072 262144 
net.ipv4.udp_mem = 65536 131072 262144 

### Set the max OS send buffer size (wmem) and receive buffer
# size (rmem) to 12 MB for queues on all protocols. In other 
# words set the amount of memory that is allocated for each
# TCP socket when it is opened or created while transferring files

# Default Socket Receive Buffer 
net.core.rmem_default = 25165824 

# Maximum Socket Receive Buffer 
net.core.rmem_max = 25165824 

# Increase the read-buffer space allocatable (minimum size, 
# initial size, and maximum size in bytes) 
net.ipv4.tcp_rmem = 20480 12582912 25165824 
net.ipv4.udp_rmem_min = 16384 

# Default Socket Send Buffer 
net.core.wmem_default = 25165824 

# Maximum Socket Send Buffer 
net.core.wmem_max = 25165824 

# Increase the write-buffer-space allocatable 
net.ipv4.tcp_wmem = 20480 12582912 25165824 
net.ipv4.udp_wmem_min = 16384 

# Increase the tcp-time-wait buckets pool size to prevent simple DOS attacks 
net.ipv4.tcp_max_tw_buckets = 1440000 
# net.ipv4.tcp_tw_recycle = 1 
net.ipv4.tcp_tw_reuse = 1