I have an array of EC2 t1.micro instances behind a load balancer and each node can manage ~100 concurrent users before it starts to get wonky.

i would THINK if i have 2 such instances it would allow my network to manage 200 concurrent users... apparently not. When i really slam the server (blitz.io) with a full 275 concurrents, it behaves the same as if there is just one node. it goes from 400ms response time to 1.6 seconds (which for a single t1.micro is expected, but not 6).

So the question is, am i simply not doing something right or is ELB effectively worthless? Anyone have some wisdom on this?

AB logs:
Loadbalancer (3x m1.medium)
Document Path:          /ping/index.html
Document Length:        185 bytes

Concurrency Level:      100
Time taken for tests:   11.668 seconds
Complete requests:      50000
Failed requests:        0
Write errors:           0
Non-2xx responses:      50001
Total transferred:      19850397 bytes
HTML transferred:       9250185 bytes
Requests per second:    4285.10 [#/sec] (mean)
Time per request:       23.337 [ms] (mean)
Time per request:       0.233 [ms] (mean, across all concurrent requests)
Transfer rate:          1661.35 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        1    2   4.3      2      63
Processing:     2   21  15.1     19     302
Waiting:        2   21  15.0     19     261
Total:          3   23  15.7     21     304

Single instance (1x m1.medium direct connection)

Document Path:          /ping/index.html
Document Length:        185 bytes

Concurrency Level:      100
Time taken for tests:   9.597 seconds
Complete requests:      50000
Failed requests:        0
Write errors:           0
Non-2xx responses:      50001
Total transferred:      19850397 bytes
HTML transferred:       9250185 bytes
Requests per second:    5210.19 [#/sec] (mean)
Time per request:       19.193 [ms] (mean)
Time per request:       0.192 [ms] (mean, across all concurrent requests)
Transfer rate:          2020.01 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        1    9 128.9      3    3010
Processing:     1   10   8.7      9     141
Waiting:        1    9   8.7      8     140
Total:          2   19 129.0     12    3020