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Re: [Linux-cluster] GFS or Web Server Performance issues?

I think a part of the problem is perception. Clustering in most cases leads to _LOWER_ performance on I/O bound processes. If it's CPU bound, then sure, it'll help. But on I/O it'll likely do you harm. It's more about redundancy and graceful degradation than performance. There's no way of getting away from the fact that a cluster has to do more work than a single node, just because it has to keep itself in sync.

The only way clustering will give you scaleable performance benefit is with partitioned (as opposed to shared) data. Shared data clustering is about convenience and redundancy, not about performance.


On Tue, 27 Nov 2007, isplist logicore net wrote:

Using a load balancer in front of GFS nodes is tricky. Make sure to set
your scheduling rule (or whatever it is called in LVS) in such a way

Do you mean such as a session, so that the user is not moved between servers?
That's something I did take into account when building the LVS LB's. I also
have tested with the LVS and direct to the web nodes. The performance is just
not what I expected but mind you, I've not done any fine tuning yet.

Are there a series of steps I should be taking? I see a lot on the net but
it's not too clear which things I really should try doing first.


that it would not generate un-necessary lock traffic. For example, you
don't want the same write lock to get rotated between three nodes. Be
aware that moving a write lock between nodes requires many steps that
include a disk flush.

-- Wendy

These are pretty much default apache RPM versions out of the box.

# ab -kc 50 -t 30
This is ApacheBench, Version 2.0.41-dev <$Revision: 1.141 $> apache-2.0
Copyright (c) 1996 Adam Twiss, Zeus Technology Ltd,
Copyright (c) 1998-2002 The Apache Software Foundation,

Benchmarking (be patient)
Finished 130 requests

Server Software:        Apache
Server Hostname:
Server Port:            80

Document Path:          /
Document Length:        8997 bytes

Concurrency Level:      50
Time taken for tests:   30.234185 seconds
Complete requests:      130
Failed requests:        0
Write errors:           0
Keep-Alive requests:    0
Total transferred:      1371090 bytes
HTML transferred:       1299586 bytes
Requests per second:    4.30 [#/sec] (mean)
Time per request:       11628.532 [ms] (mean)
Time per request:       232.571 [ms] (mean, across all concurrent
Transfer rate:          44.25 [Kbytes/sec] received

Connection Times (ms)
min  mean[+/-sd] median   max
Connect:        0    1   1.4      2       4
Processing:   409 6228 4357.5   5227   16317
Waiting:      369 6146 4370.8   5199   16261
Total:        409 6230 4358.1   5230   16321

Percentage of the requests served within a certain time (ms)
50%   5230
66%   8331
75%   9310
80%  10386
90%  12820
95%  14502
98%  15399
99%  15746
100%  16321 (longest request)

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