String as value on Graphite message

Hi,
I'm quite new to Graphite - Grafana, recently I had the necessity to show a single panel stat exposing the value 0|1|2 if the website "state" is ok, some issue, heavy issues, so after a deploy I run ann healtcheck done on my server I send a message to graphite such as:

servers.serverx.status 0 timestamp
this let me get info from grafana and light a green box if current value is 0.

What I want to do now is add a stat that let me show which is the deploy commit that let the server be "green,yellow or red"
I tried to send a message like
servers.serverx.commithash 4dsa6k5 timestamp
but of course, even if I run on my graphite server
http://127.0.0.1/render/?target=servers.serverx.commithash&from=-1h&to=now&rawData=true
I cannot get the string info, only numbers or None, as this example:

servers.serverx.commithash,1461835500,1461839100,60|None,None,None,None,2.0,None,None,None,None,None,None,None,None,None,None,None,None,None,None,None,None,None,None,None,None,55.0,None,None,None,None,None,None,None,None

Is this a Graphite limitation? is there a way to use String as Value in the message?

Thanks a lot.