Database Reference
In-Depth Information
2.0
1.8
1.6
1.4
1.2
1.0
Consistent - 99% read
Consistent - 75% read
Consistent - 50% read
Eventual Consistent - 99% read
Eventual Consistent - 75% read
Eventual Consistent - 50% read
0.8
0.6
0.4
0.2
0.0
0
500
1000
1500
2000
2500
Number of Emulated Clients (Threads)
Fig. 5.5
Response time of reads at various read/write ratios on Amazon SimpleDB
3.0
2.5
2.0
1.5
Consistent - 99% read
Consistent - 75% read
Consistent - 50% read
Eventual Consistent - 99% read
Eventual Consistent - 75% read
Eventual Consistent - 50% read
1.0
0.5
0.0
0
500
1000
1500
2000
2500
Number of Emulated Clients (Threads)
Fig. 5.6
Response time of writes at various read/write ratios on Amazon SimpleDB
with this number of end-users. As the response time increased, each end-user
sent less than one request every second and, therefore, the throughput percentage
decreased.
It must be noted that Amazon SimpleDB often returns exceptions with status
code 503, representing “Service is currently unavailable”, under heavy load.
Figure
5.9
shows the average failure rates of eventual consistent reads and consistent
reads, with each data point being marked with whiskers to highlight the correspond-
ing maximum and minimum failure rates. Clearly the failure rate increased as the
load increased, but again the observation is that eventual consistent read does less
well than consistent read, although the difference is not significant.
