Coyote Point Systems Equalizer, Руководство по установке и администрированию

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Chapter 5: Administering Virtual Clusters
78 Equalizer Installation and Administration Guide
their performance. You should adjust server weights by small increments—for example,
you might set the static weight of one server to 110 and the other to 90. Fine-tuning the
server weights to match each server’s actual capability can easily improve your cluster’s
response time by 5 to 10%.
Setting Static Weights for Mixed Clusters
Equalizer enables you to build heterogeneous clusters using servers of widely varying
capabilities. You adjust for the differences by assigning static weights that correspond to
the relative capabilities of the available servers. This enables you to get the most out of
your existing hardware—an older server can be used side-by-side with the most recent
server hardware available.
After you assign relative static weights, you should monitor cluster performance for two to
three hours under load. It will probably take two or three iterations to fine-tune the
weights and optimize performance of your cluster.
Continue monitoring the performance of your cluster and servers and watch for any
trends. For example, if you notice that Equalizer always adjusts the dynamic weights so
that the weight of one server is far below 100 and the weight of another is far above 100,
there might be a problem with the server whose dynamic weight is consistently being
reduced.
Shutting Down a Server Gracefully
To avoid interrupting user sessions, you need to make sure that the server no longer has
any active connections before you shut it down or delete it from a cluster. When a server’s
static weight is set to zero, Equalizer will not send any new requests to that server.
Connections that are already established continue to exist until the client and server
application end them or they time out because they are idle.
To shut down servers in a generic TCP or UDP (L4) cluster, you can just set the server’s
weight to zero and wait for the existing connections to terminate. However, you need to
quiesce severs in HTTP and HTTPS (L7) clusters to enable severs to finish processing
requests for clients that have a persistent session with the server. When a server is
quiesced, no new connections from new clients are routed to the server, but requests from
clients with persistent session with the server will still be sent to the server. Once all of the
persistent sessions on the server have expired, you can set the server’s static weight to zero
so that no additional requests sill be sent to the server.
When you are deleting a server or need to remove a server from service for maintenance:
1. If server belongs to an L7 cluster that supports persistent sessions:
a. In the left frame, click the name of the server you want to quiesce. The Server
Parameters are displayed in the right frame.
b. Select Change Server Parameters from the local menu in the Server Parameters
frame. The Change Server Parameters dialog is displayed in the right frame.
Note – Equalizer’s ALB algorithm can take 10-15 minutes to fine-tune cluster performance when
static weights are changed. After changing static weights, wait half an hour before judging the
ALB performance of the cluster.