improve database design for monitoring application I need assistance with my DB design, I have a monitoring script that produce the following data every minute , and produce stats about virtual machine performance. 

Array
(
    [timestamp] =&gt; 2015-05-05T18:11:00Z
    [vm_name] =&gt; i-2-20-VM
    [memory_internal_free] =&gt; 3516900
    [vbd_xvdd_read] =&gt; 0
    [vbd_xvdd_write] =&gt; 0
    [vif_0_rx] =&gt; 0
    [vif_0_tx] =&gt; 0
    [memory] =&gt; 4294967296
    [vbd_xvda_read] =&gt; 0
    [vbd_xvda_write] =&gt; 0
    [cpu0] =&gt; 0.000100
    [cpu1] =&gt; 0.000100
)
Array
(
    [timestamp] =&gt; 2015-05-05T18:11:00Z
    [vm_name] =&gt; i-2-24-VM
    [memory_target] =&gt; 4294967296
    [vbd_xvdb_read] =&gt; 0
    [vbd_xvdb_write] =&gt; 0
    [vbd_xvda_read] =&gt; 0
    [vbd_xvda_write] =&gt; 0
    [vif_0_rx] =&gt; 0
    [vif_0_tx] =&gt; 0
    [memory] =&gt; 4294967296
    [cpu0] =&gt; 0.000100
    [cpu1] =&gt; 0.000100
)


I'm trying to store the following info into my database, I have create single table 

I have created table as follows 

CREATE TABLE `md_metrics_status` (
  `id` int(100) NOT NULL AUTO_INCREMENT,
  `timestamp` datetime NOT NULL,
  `vm_name` varchar(50) DEFAULT NULL,
  `memory_target` varchar(255) DEFAULT NULL,
  `vif_2_rx` varchar(255) DEFAULT NULL,
  `vif_2_tx` varchar(255) DEFAULT NULL,
  `memory` varchar(255) DEFAULT NULL,
  `vbd_xvda_read` varchar(255) DEFAULT NULL,
  `vbd_xvda_write` varchar(255) DEFAULT NULL,
  `vbd_xvdd_read` varchar(255) DEFAULT NULL,
  `vbd_xvdd_write` varchar(255) DEFAULT NULL,
  `vif_1_rx` varchar(255) DEFAULT NULL,
  `vif_1_tx` varchar(255) DEFAULT NULL,
  `vif_0_rx` varchar(255) DEFAULT NULL,
  `vif_0_tx` varchar(255) DEFAULT NULL,
  `cpu0` varchar(255) DEFAULT NULL,
  `cpu1` varchar(255) DEFAULT NULL,
  `vif_3_rx` varchar(255) DEFAULT NULL,
  `vif_3_tx` varchar(255) DEFAULT NULL,
  `memory_internal_free` varchar(255) DEFAULT NULL,
  `vbd_xvdb_read` varchar(255) DEFAULT NULL,
  `vbd_xvdb_write` varchar(255) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=162339 DEFAULT CHARSET=utf8


Now this table has grown so large, and searching for records between specific timestamps is very slow. 

I'm unable to add an index on timestamp field, because I get many duplicate records, as you can see in the example. 

What is wrong with this table design? how can I improve this setup? 

I have full control over the database, and over the script that produces the data. 

Your input is highly appreciated. 

Thank you
Add an index, not a unique key:

ALTER TABLE md_metrics_status ADD INDEX (`timestamp`);


I believe you are using PHPMyAdmin to add the index, and in PMA, unique is the default choice when you want to add an index, and that is why you are getting the duplicate key error.