We are tracking internet down time at our stores. Basically every 15 minutes we receive a list of all stores that are currently up. I then process that and for every store that was missing in the list I store a record in a dataset with the store and a timestamp. We need to show over a 24 hour time period what stores were down and when that occurred. My thought was to display something like this:

It would actually cover the most recent rolling 24 hours in 15 minute increments (another version would show the previous day fixed from midnight to midnight). Green for up, red for down.

Is there a chart type that can display data like this? If so, can it display from a dataset that has one row per store that is down per 15 minute increment, or should I use an ETL to make a summary dataset with one row per store and one column per increment?