Table of Contents
Advertisement
Chapter 1. Linux Virtual Server Overview
Weighted Round-Robin Scheduling
Distributes each request sequentially around the pool of real servers but gives more jobs to
servers with greater capacity. Capacity is indicated by a user-assigned weight factor, which
is then adjusted upward or downward by dynamic load information. Refer to
"Server Weight and Scheduling"
Weighted round-robin scheduling is a preferred choice if there are significant differences in
the capacity of real servers in the pool. However, if the request load varies dramatically, the
more heavily weighted server may answer more than its share of requests.
Least-Connection
Distributes more requests to real servers with fewer active connections. Because it keeps
track of live connections to the real servers through the IPVS table, least-connection is a
type of dynamic scheduling algorithm, making it a better choice if there is a high degree of
variation in the request load. It is best suited for a real server pool where each member
node has roughly the same capacity. If a group of servers have different capabilities,
weighted least-connection scheduling is a better choice.
Weighted Least-Connections (default)
Distributes more requests to servers with fewer active connections relative to their
capacities. Capacity is indicated by a user-assigned weight, which is then adjusted upward
or downward by dynamic load information. The addition of weighting makes this algorithm
ideal when the real server pool contains hardware of varying capacity. Refer to
"Server Weight and Scheduling"
Locality-Based Least-Connection Scheduling
Distributes more requests to servers with fewer active connections relative to their
destination IPs. This algorithm is designed for use in a proxy-cache server cluster. It routes
the packets for an IP address to the server for that address unless that server is above its
capacity and has a server in its half load, in which case it assigns the IP address to the least
loaded real server.
Locality-Based Least-Connection Scheduling with Replication Scheduling
Distributes more requests to servers with fewer active connections relative to their
destination IPs. This algorithm is also designed for use in a proxy-cache server cluster. It
differs from Locality-Based Least-Connection Scheduling by mapping the target IP address
to a subset of real server nodes. Requests are then routed to the server in this subset with
the lowest number of connections. If all the nodes for the destination IP are above capacity,
it replicates a new server for that destination IP address by adding the real server with the
least connections from the overall pool of real servers to the subset of real servers for that
destination IP. The most loaded node is then dropped from the real server subset to prevent
over-replication.
Destination Hash Scheduling
Distributes requests to the pool of real servers by looking up the destination IP in a static
hash table. This algorithm is designed for use in a proxy-cache server cluster.
Source Hash Scheduling
6
for more on weighting real servers.
for more on weighting real servers.
Section 3.2,
Section 3.2,
Advertisement
Table of Contents
