User guide

17-26 E
XTREME
W
ARE
S
OFTWARE
U
SER
G
UIDE
S
ERVER
L
OAD
B
ALANCING
(SLB)
P
ERSISTENCE
Using persistence, you can ensure that traffic flows do not span multiple servers. The
switch supports two types of persistence:
• Client persistence
• Sticky persistence
C
LIENT
P
ERSISTENCE
Client persistence for a virtual server provides a persist mask feature. You can define a
range of IP addresses that can be matched to a persistent connection. Any client whose
source IP address falls within the range is considered a match for the given persistence
entry.
To configure client persistence, use this command:
enable slb vip [<vipname> | all] client-persistence {timeout <seconds>}
{mask <mask>}
S
TICKY
P
ERSISTENCE
Sticky persistence provides a special type of persistence that is especially useful for
cache servers. Similar to client persistence, sticky persistence keeps track of incoming
clients’ source and destination IP addresses. When a client is looking to make a repeat
connection to a particular destination IP address, the switch directs the client to the
same cache server or other transparent node that it previously used. Allowing clients to
repeatedly use the same cache server can help you reduce the amount of content that
might otherwise be duplicated on two or more cache servers in your network.
Sticky persistence provides the most benefits when you load balance caching proxy
servers. A caching proxy server intercepts web requests and returns a cached web page
if it is available. In order to improve the efficiency of the cache on these proxies, it is
necessary to send similar requests to the same proxy server repeatedly. Sticky
persistence can be used to cache a given web page on one proxy server instead of on
every proxy server in an array. This saves the other proxies from having to duplicate the
web page in their cache, wasting memory.
In order to prevent sticky entries from clumping on one server, use a static load
balancing mode, such as round-robin.