Sun Microsystems SunLink SNA 9.1 PU2.1, Руководство по настройке

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Load Balancing E-7
E
Refer to Figure E-1 on page E-3 as you follow the procedure.
1. A client requests a connection to the domain, using the geographical load
balancing keyword (
glb
). The connection request is handled by DNS and
sent to SunGMAN for name resolution.
A sample connection request is as follows:
suntn3270x -h glb.sna.sun.com
2. SunGMAN looks for a user record with either an IP Address parameter or
an IP Hostname parameter that matches the IP address of the system that
sent the connection request. Note that the connection request is sent to the
SunGMAN by the DNS, not by the client.
If the SunGMAN finds a matching user record, it considers the first
(preferred) default resource in the list of default resources. Because each site
has its own secondary DNS, SunGMAN finds user record
SITE1
for clients
at site 1 and user record
SITE2
for clients at site 2. Therefore, for clients at
site 1, the preferred resource is
POOL-1
and for clients at site 2, the preferred
resource is
POOL-2
. In both cases, the preferred resource contains LUs that
are geographically closest to the client.
If the preferred LU pool is distributed across multiple systems and more
than one system has an available LU, SunGMAN selects the system with the
lowest system load average and the highest bandwidth.
If an LU is not available in the preferred LU pool, SunGMAN considers the
next (alternate) default resource in the list (
POOL-2
for clients at site 1 and
POOL-1
for clients at site 2). If the alternate LU pool is distributed across
multiple systems and more than one system has an available LU,
SunGMAN selects the system with the lowest system load average and the
highest bandwidth.
If no active LUs are found in either LU pool, SunGMAN returns to the
preferred LU pool and searches both LU pools again, this time allowing
inactive LUs to satisfy the request.
If the second pass is unsuccessful, SunGMAN selects the “least recently
used” system for the preferred resource.
3. SunGMAN returns the IP address of the system with the best LU for the
connection to DNS.
4. DNS returns the IP address of the system that has the best LU for this
connection to the requesting client.